diff --git a/src/prism.c b/src/prism.c
index a68577b4dce..69f896cbb6b 100644
--- a/src/prism.c
+++ b/src/prism.c
@@ -5475,46 +5475,40 @@ pm_super_node_create(pm_parser_t *parser, const pm_token_t *keyword, pm_argument
  * Read through the contents of a string and check if it consists solely of US ASCII code points.
  */
 static bool
-ascii_only_p( const pm_string_t *contents) {
-    const size_t length = contents->length;
+pm_ascii_only_p(const pm_string_t *contents) {
+    const size_t length = pm_string_length(contents);
+    const uint8_t *source = pm_string_source(contents);
 
-    for (size_t i = 0; i < length; i++) {
-        if (contents->source[i] & 0x80) {
-            return false;
-        }
+    for (size_t index = 0; index < length; index++) {
+        if (source[index] & 0x80) return false;
     }
 
     return true;
 }
 
 /**
- * Ruby "downgrades" the encoding of Symbols to US-ASCII if the associated encoding is ASCII-compatible and
- * the Symbol consists only of US-ASCII code points. Otherwise, the encoding may be explicitly set with an
- * escape sequence.
+ * Ruby "downgrades" the encoding of Symbols to US-ASCII if the associated
+ * encoding is ASCII-compatible and the Symbol consists only of US-ASCII code
+ * points. Otherwise, the encoding may be explicitly set with an escape
+ * sequence.
  */
 static inline pm_node_flags_t
 parse_symbol_encoding(const pm_parser_t *parser, const pm_string_t *contents) {
-    // Don't set any flags on the Symbol if it hasn't been populated yet.
-    if (contents->source == NULL) {
-        return 0;
-    }
-
-    // Ruby stipulates that all source files must use an ASCII-compatible encoding. Thus, all symbols appearing in
-    // source are eligible for "downgrading" to US-ASCII.
-    if (ascii_only_p(contents)) {
-        return PM_SYMBOL_FLAGS_FORCED_US_ASCII_ENCODING;
-    } else {
-        // A Symbol may optionally have its encoding explicitly set.
-        //
-        // NB: an explicitly set encoding is ignored by Ruby if the Symbol consists of only US ASCII code points.
-        if (parser->explicit_encoding != NULL) {
-            if (parser->explicit_encoding == PM_ENCODING_UTF_8_ENTRY) {
-                return PM_SYMBOL_FLAGS_FORCED_UTF8_ENCODING;
-            } else if (parser->encoding == PM_ENCODING_US_ASCII_ENTRY) {
-                return PM_SYMBOL_FLAGS_FORCED_BINARY_ENCODING;
-            }
+    if (parser->explicit_encoding != NULL) {
+        // A Symbol may optionally have its encoding explicitly set. This will
+        // happen if an escape sequence results in a non-ASCII code point.
+        if (parser->explicit_encoding == PM_ENCODING_UTF_8_ENTRY) {
+            return PM_SYMBOL_FLAGS_FORCED_UTF8_ENCODING;
+        } else if (parser->encoding == PM_ENCODING_US_ASCII_ENTRY) {
+            return PM_SYMBOL_FLAGS_FORCED_BINARY_ENCODING;
         }
+    } else if (pm_ascii_only_p(contents)) {
+        // Ruby stipulates that all source files must use an ASCII-compatible
+        // encoding. Thus, all symbols appearing in source are eligible for
+        // "downgrading" to US-ASCII.
+        return PM_SYMBOL_FLAGS_FORCED_US_ASCII_ENCODING;
     }
+
     return 0;
 }
 
@@ -5523,13 +5517,13 @@ parse_symbol_encoding(const pm_parser_t *parser, const pm_string_t *contents) {
  * string.
  */
 static pm_symbol_node_t *
-pm_symbol_node_create_unescaped(pm_parser_t *parser, const pm_token_t *opening, const pm_token_t *value, const pm_token_t *closing, const pm_string_t *unescaped) {
+pm_symbol_node_create_unescaped(pm_parser_t *parser, const pm_token_t *opening, const pm_token_t *value, const pm_token_t *closing, const pm_string_t *unescaped, pm_node_flags_t flags) {
     pm_symbol_node_t *node = PM_ALLOC_NODE(parser, pm_symbol_node_t);
 
     *node = (pm_symbol_node_t) {
         {
             .type = PM_SYMBOL_NODE,
-            .flags = PM_NODE_FLAG_STATIC_LITERAL,
+            .flags = PM_NODE_FLAG_STATIC_LITERAL | flags,
             .location = {
                 .start = (opening->type == PM_TOKEN_NOT_PROVIDED ? value->start : opening->start),
                 .end = (closing->type == PM_TOKEN_NOT_PROVIDED ? value->end : closing->end)
@@ -5541,8 +5535,6 @@ pm_symbol_node_create_unescaped(pm_parser_t *parser, const pm_token_t *opening,
         .unescaped = *unescaped
     };
 
-    pm_node_flag_set((pm_node_t *)node, parse_symbol_encoding(parser, unescaped));
-
     return node;
 }
 
@@ -5551,7 +5543,7 @@ pm_symbol_node_create_unescaped(pm_parser_t *parser, const pm_token_t *opening,
  */
 static inline pm_symbol_node_t *
 pm_symbol_node_create(pm_parser_t *parser, const pm_token_t *opening, const pm_token_t *value, const pm_token_t *closing) {
-    return pm_symbol_node_create_unescaped(parser, opening, value, closing, &PM_STRING_EMPTY);
+    return pm_symbol_node_create_unescaped(parser, opening, value, closing, &PM_STRING_EMPTY, 0);
 }
 
 /**
@@ -5559,7 +5551,7 @@ pm_symbol_node_create(pm_parser_t *parser, const pm_token_t *opening, const pm_t
  */
 static pm_symbol_node_t *
 pm_symbol_node_create_current_string(pm_parser_t *parser, const pm_token_t *opening, const pm_token_t *value, const pm_token_t *closing) {
-    pm_symbol_node_t *node = pm_symbol_node_create_unescaped(parser, opening, value, closing, &parser->current_string);
+    pm_symbol_node_t *node = pm_symbol_node_create_unescaped(parser, opening, value, closing, &parser->current_string, parse_symbol_encoding(parser, &parser->current_string));
     parser->current_string = PM_STRING_EMPTY;
     return node;
 }
@@ -5581,7 +5573,8 @@ pm_symbol_node_label_create(pm_parser_t *parser, const pm_token_t *token) {
 
             assert((label.end - label.start) >= 0);
             pm_string_shared_init(&node->unescaped, label.start, label.end);
-            pm_node_flag_set((pm_node_t *)node, parse_symbol_encoding(parser, &node->unescaped));
+            pm_node_flag_set((pm_node_t *) node, parse_symbol_encoding(parser, &node->unescaped));
+
             break;
         }
         case PM_TOKEN_MISSING: {
@@ -12644,12 +12637,15 @@ PM_STATIC_ASSERT(__LINE__, ((int) PM_STRING_FLAGS_FORCED_UTF8_ENCODING) == ((int
 static inline pm_node_flags_t
 parse_unescaped_encoding(const pm_parser_t *parser) {
     if (parser->explicit_encoding != NULL) {
-        // If the there's an explicit encoding and it's using a UTF-8 escape sequence, then mark the string as UTF-8.
         if (parser->explicit_encoding == PM_ENCODING_UTF_8_ENTRY) {
+            // If the there's an explicit encoding and it's using a UTF-8 escape
+            // sequence, then mark the string as UTF-8.
             return PM_STRING_FLAGS_FORCED_UTF8_ENCODING;
-        // If there's a non-UTF-8 escape sequence being used, then the string uses the source encoding, unless the source
-        // is marked as US-ASCII. In that case the string is forced as ASCII-8BIT in order to keep the string valid.
         } else if (parser->encoding == PM_ENCODING_US_ASCII_ENTRY) {
+            // If there's a non-UTF-8 escape sequence being used, then the
+            // string uses the source encoding, unless the source is marked as
+            // US-ASCII. In that case the string is forced as ASCII-8BIT in
+            // order to keep the string valid.
             return PM_STRING_FLAGS_FORCED_BINARY_ENCODING;
         }
     }
@@ -12801,7 +12797,8 @@ parse_operator_symbol(pm_parser_t *parser, const pm_token_t *opening, pm_lex_sta
     parser_lex(parser);
 
     pm_string_shared_init(&symbol->unescaped, parser->previous.start, end);
-    pm_node_flag_set((pm_node_t *)symbol, parse_symbol_encoding(parser, &symbol->unescaped));
+    pm_node_flag_set((pm_node_t *) symbol, PM_SYMBOL_FLAGS_FORCED_US_ASCII_ENCODING);
+
     return (pm_node_t *) symbol;
 }
 
@@ -12840,7 +12837,7 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
         pm_symbol_node_t *symbol = pm_symbol_node_create(parser, &opening, &parser->previous, &closing);
 
         pm_string_shared_init(&symbol->unescaped, parser->previous.start, parser->previous.end);
-        pm_node_flag_set((pm_node_t *)symbol, parse_symbol_encoding(parser, &symbol->unescaped));
+        pm_node_flag_set((pm_node_t *) symbol, parse_symbol_encoding(parser, &symbol->unescaped));
 
         return (pm_node_t *) symbol;
     }
@@ -12927,7 +12924,6 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
     } else {
         content = (pm_token_t) { .type = PM_TOKEN_STRING_CONTENT, .start = parser->previous.end, .end = parser->previous.end };
         pm_string_shared_init(&unescaped, content.start, content.end);
-
     }
 
     if (next_state != PM_LEX_STATE_NONE) {
@@ -12940,10 +12936,7 @@ parse_symbol(pm_parser_t *parser, pm_lex_mode_t *lex_mode, pm_lex_state_t next_s
         expect1(parser, PM_TOKEN_STRING_END, PM_ERR_SYMBOL_TERM_DYNAMIC);
     }
 
-    pm_symbol_node_t *symbol_node = pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped);
-    pm_node_flag_set((pm_node_t *)symbol_node, parse_symbol_encoding(parser, &symbol_node->unescaped));
-
-    return (pm_node_t *) symbol_node;
+    return (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped, parse_symbol_encoding(parser, &unescaped));
 }
 
 /**
@@ -12968,6 +12961,8 @@ parse_undef_argument(pm_parser_t *parser) {
             pm_symbol_node_t *symbol = pm_symbol_node_create(parser, &opening, &parser->previous, &closing);
 
             pm_string_shared_init(&symbol->unescaped, parser->previous.start, parser->previous.end);
+            pm_node_flag_set((pm_node_t *) symbol, parse_symbol_encoding(parser, &symbol->unescaped));
+
             return (pm_node_t *) symbol;
         }
         case PM_TOKEN_SYMBOL_BEGIN: {
@@ -13007,7 +13002,8 @@ parse_alias_argument(pm_parser_t *parser, bool first) {
             pm_symbol_node_t *symbol = pm_symbol_node_create(parser, &opening, &parser->previous, &closing);
 
             pm_string_shared_init(&symbol->unescaped, parser->previous.start, parser->previous.end);
-            pm_node_flag_set((pm_node_t *)symbol, parse_symbol_encoding(parser, &symbol->unescaped));
+            pm_node_flag_set((pm_node_t *) symbol, parse_symbol_encoding(parser, &symbol->unescaped));
+
             return (pm_node_t *) symbol;
         }
         case PM_TOKEN_SYMBOL_BEGIN: {
@@ -14066,7 +14062,7 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
                 expect1(parser, PM_TOKEN_STRING_END, PM_ERR_STRING_LITERAL_TERM);
                 node = (pm_node_t *) pm_interpolated_string_node_create(parser, &opening, &parts, &parser->previous);
             } else if (accept1(parser, PM_TOKEN_LABEL_END) && !state_is_arg_labeled) {
-                node = (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped);
+                node = (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped, parse_symbol_encoding(parser, &unescaped));
             } else if (match1(parser, PM_TOKEN_EOF)) {
                 pm_parser_err_token(parser, &opening, PM_ERR_STRING_LITERAL_TERM);
                 node = (pm_node_t *) pm_string_node_create_unescaped(parser, &opening, &content, &parser->current, &unescaped);
@@ -14088,7 +14084,7 @@ parse_strings(pm_parser_t *parser, pm_node_t *current) {
                 pm_node_flag_set(node, parse_unescaped_encoding(parser));
                 expect1(parser, PM_TOKEN_STRING_END, PM_ERR_STRING_LITERAL_TERM);
             } else if (accept1(parser, PM_TOKEN_LABEL_END)) {
-                node = (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped);
+                node = (pm_node_t *) pm_symbol_node_create_unescaped(parser, &opening, &content, &parser->previous, &unescaped, parse_symbol_encoding(parser, &unescaped));
             } else {
                 // If we get here, then we have interpolation so we'll need
                 // to create a string or symbol node with interpolation.
diff --git a/test/prism/snapshots/undef.txt b/test/prism/snapshots/undef.txt
index fb62b9acb52..3430ef50599 100644
--- a/test/prism/snapshots/undef.txt
+++ b/test/prism/snapshots/undef.txt
@@ -6,7 +6,7 @@
         ├── @ UndefNode (location: (1,0)-(1,7))
         │   ├── names: (length: 1)
         │   │   └── @ SymbolNode (location: (1,6)-(1,7))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: forced_us_ascii_encoding
         │   │       ├── opening_loc: ∅
         │   │       ├── value_loc: (1,6)-(1,7) = "a"
         │   │       ├── closing_loc: ∅
@@ -15,13 +15,13 @@
         ├── @ UndefNode (location: (3,0)-(3,10))
         │   ├── names: (length: 2)
         │   │   ├── @ SymbolNode (location: (3,6)-(3,7))
-        │   │   │   ├── flags: ∅
+        │   │   │   ├── flags: forced_us_ascii_encoding
         │   │   │   ├── opening_loc: ∅
         │   │   │   ├── value_loc: (3,6)-(3,7) = "a"
         │   │   │   ├── closing_loc: ∅
         │   │   │   └── unescaped: "a"
         │   │   └── @ SymbolNode (location: (3,9)-(3,10))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: forced_us_ascii_encoding
         │   │       ├── opening_loc: ∅
         │   │       ├── value_loc: (3,9)-(3,10) = "b"
         │   │       ├── closing_loc: ∅
@@ -30,7 +30,7 @@
         ├── @ UndefNode (location: (5,0)-(5,8))
         │   ├── names: (length: 1)
         │   │   └── @ SymbolNode (location: (5,6)-(5,8))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: forced_us_ascii_encoding
         │   │       ├── opening_loc: ∅
         │   │       ├── value_loc: (5,6)-(5,8) = "if"
         │   │       ├── closing_loc: ∅
@@ -108,7 +108,7 @@
         └── @ UndefNode (location: (17,0)-(17,14))
             ├── names: (length: 1)
             │   └── @ SymbolNode (location: (17,6)-(17,14))
-            │       ├── flags: ∅
+            │       ├── flags: forced_us_ascii_encoding
             │       ├── opening_loc: ∅
             │       ├── value_loc: (17,6)-(17,14) = "Constant"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/unparser/corpus/semantic/undef.txt b/test/prism/snapshots/unparser/corpus/semantic/undef.txt
index 1578260a64f..ecb073148d7 100644
--- a/test/prism/snapshots/unparser/corpus/semantic/undef.txt
+++ b/test/prism/snapshots/unparser/corpus/semantic/undef.txt
@@ -6,7 +6,7 @@
         ├── @ UndefNode (location: (1,0)-(1,9))
         │   ├── names: (length: 1)
         │   │   └── @ SymbolNode (location: (1,6)-(1,9))
-        │   │       ├── flags: ∅
+        │   │       ├── flags: forced_us_ascii_encoding
         │   │       ├── opening_loc: ∅
         │   │       ├── value_loc: (1,6)-(1,9) = "foo"
         │   │       ├── closing_loc: ∅
@@ -15,13 +15,13 @@
         └── @ UndefNode (location: (2,0)-(2,14))
             ├── names: (length: 2)
             │   ├── @ SymbolNode (location: (2,6)-(2,9))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: forced_us_ascii_encoding
             │   │   ├── opening_loc: ∅
             │   │   ├── value_loc: (2,6)-(2,9) = "foo"
             │   │   ├── closing_loc: ∅
             │   │   └── unescaped: "foo"
             │   └── @ SymbolNode (location: (2,11)-(2,14))
-            │       ├── flags: ∅
+            │       ├── flags: forced_us_ascii_encoding
             │       ├── opening_loc: ∅
             │       ├── value_loc: (2,11)-(2,14) = "bar"
             │       ├── closing_loc: ∅
diff --git a/test/prism/snapshots/whitequark/undef.txt b/test/prism/snapshots/whitequark/undef.txt
index 0f735cc7631..9889a5a5257 100644
--- a/test/prism/snapshots/whitequark/undef.txt
+++ b/test/prism/snapshots/whitequark/undef.txt
@@ -6,7 +6,7 @@
         └── @ UndefNode (location: (1,0)-(1,27))
             ├── names: (length: 3)
             │   ├── @ SymbolNode (location: (1,6)-(1,9))
-            │   │   ├── flags: ∅
+            │   │   ├── flags: forced_us_ascii_encoding
             │   │   ├── opening_loc: ∅
             │   │   ├── value_loc: (1,6)-(1,9) = "foo"
             │   │   ├── closing_loc: ∅