diff --git a/fprettify/__init__.py b/fprettify/__init__.py
index d6450a3..01dd044 100644
--- a/fprettify/__init__.py
+++ b/fprettify/__init__.py
@@ -470,9 +470,8 @@ def build_scope_parser(fypp=True, mod=True):
 F90_NUMBER_ALL_RE = "(" + F90_NUMBER_RE + "|" + F90_FLOAT_EXP_RE + ")"
 F90_NUMBER_ALL_REC = re.compile(F90_NUMBER_ALL_RE, RE_FLAGS)
 
-## F90_CONSTANTS_TYPES_RE = re.compile(r"\b" + F90_NUMBER_ALL_RE + "_(" + "|".join([a + r"\b" for a in (
 F90_CONSTANTS_TYPES_RE = re.compile(
-    r"(" + F90_NUMBER_ALL_RE + ")*_(" + "|".join((
+    r"(" + F90_NUMBER_ALL_RE + ")_(" + "|".join((
     ## F2003 iso_fortran_env constants.
     ## F2003 iso_c_binding constants.
     "c_int", "c_short", "c_long", "c_long_long", "c_signed_char",