diff --git a/bindings/go/scip/parse.go b/bindings/go/scip/parse.go
index 4e7310a4..048ecac1 100644
--- a/bindings/go/scip/parse.go
+++ b/bindings/go/scip/parse.go
@@ -70,7 +70,7 @@ func (pi *IndexVisitor) ParseStreaming(r io.Reader) error {
 			}
 			// Keep going when len == 0 instead of short-circuiting to preserve empty sub-messages
 			if dataLen > 0 {
-				numRead, err := r.Read(dataBuf)
+				numRead, err := io.ReadAtLeast(r, dataBuf, dataLen)
 				if err != nil {
 					return errors.Wrapf(err, "failed to read data for %s", indexFieldName(fieldNumber))
 				}
diff --git a/bindings/go/scip/parse_test.go b/bindings/go/scip/parse_test.go
index a3a30419..a89cc7fc 100644
--- a/bindings/go/scip/parse_test.go
+++ b/bindings/go/scip/parse_test.go
@@ -2,6 +2,8 @@ package scip
 
 import (
 	"bytes"
+	"compress/gzip"
+	"os"
 	"regexp"
 	"testing"
 
@@ -46,3 +48,31 @@ func TestFuzz(t *testing.T) {
 		}
 	}
 }
+
+func TestLargeDocuments(t *testing.T) {
+	// Copied from the Sourcegraph monorepo, which triggered a bug
+	// where Reader.read() didn't actually fill a buffer completely,
+	// due to the presence of large documents.
+	gzipped, err := os.Open("./testdata/index1.scip.gz")
+	if err != nil {
+		t.Fatalf("unexpected error reading test file: %s", err)
+	}
+	reader, err := gzip.NewReader(gzipped)
+	if err != nil {
+		t.Fatalf("unexpected error unzipping test file: %s", err)
+	}
+
+	parsedIndex := Index{}
+
+	indexVisitor := IndexVisitor{func(metadata *Metadata) {
+		parsedIndex.Metadata = metadata
+	}, func(document *Document) {
+		parsedIndex.Documents = append(parsedIndex.Documents, document)
+	}, func(extSym *SymbolInformation) {
+		parsedIndex.ExternalSymbols = append(parsedIndex.ExternalSymbols, extSym)
+	}}
+
+	if err := indexVisitor.ParseStreaming(reader); err != nil {
+		t.Fatalf("got error parsing index %v", err)
+	}
+}
diff --git a/bindings/go/scip/testdata/index1.scip.gz b/bindings/go/scip/testdata/index1.scip.gz
new file mode 100644
index 00000000..fdc8979a
Binary files /dev/null and b/bindings/go/scip/testdata/index1.scip.gz differ