diff --git a/lib/paru/filter/math.rb b/lib/paru/filter/math.rb
index 41bcd57..0e64db0 100644
--- a/lib/paru/filter/math.rb
+++ b/lib/paru/filter/math.rb
@@ -44,7 +44,7 @@ def initialize(contents)
             # @return [Boolean] true if math type is "InlineMath", false
             #   otherwise
             def inline?()
-                "InlineMath" == @math_type[t]
+                "InlineMath" == @math_type["t"]
             end
 
             # Convert this Math node's content to Inline
@@ -58,7 +58,7 @@ def inline!()
             #
             # @return [Boolean] true if type is "DisplayMath"
             def display?()
-                "DisplayMath" == @math_type[t]
+                "DisplayMath" == @math_type["t"]
             end
 
             # Make this Math node's content display as a block