diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c1904f9..5bf57f07 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@
 - Updated `setup.cfg` in preparation of submitting package to `conda-forge`
 - Added `Editor Integration` section in documentation
 
+### Fixed
+
+- Fixed parsing of `defined` without by parenthesis surrounding the definition
+  ([#67](https://github.com/gnikit/fortls/pull/67))
+
 ## 2.2.4
 
 ### Fixed
diff --git a/fortls/regex_patterns.py b/fortls/regex_patterns.py
index 31de5e12..ea28afee 100644
--- a/fortls/regex_patterns.py
+++ b/fortls/regex_patterns.py
@@ -110,7 +110,7 @@ class FortranRegularExpressions:
     FREE_OPENMP: Pattern = compile(r"[ ]*!\$OMP", I)
     FREE_FORMAT_TEST: Pattern = compile(r"[ ]{1,4}[a-z]", I)
     # Preprocessor matching rules
-    DEFINED: Pattern = compile(r"defined[ ]*\([ ]*([a-z_][a-z0-9_]*)[ ]*\)", I)
+    DEFINED: Pattern = compile(r"defined[ ]*\(?[ ]*([a-z_][a-z0-9_]*)[ ]*\)?", I)
     PP_REGEX: Pattern = compile(r"#(if |ifdef|ifndef|else|elif|endif)")
     PP_DEF: Pattern = compile(r"#(define|undef)[ ]*([\w]+)(\((\w+(,[ ]*)?)+\))?", I)
     PP_DEF_TEST: Pattern = compile(r"(![ ]*)?defined[ ]*\([ ]*([a-z0-9_]*)[ ]*\)$", I)
diff --git a/test/test_preproc.py b/test/test_preproc.py
index f1472b4b..35dce5af 100644
--- a/test/test_preproc.py
+++ b/test/test_preproc.py
@@ -27,6 +27,7 @@ def check_return(result_array, checks):
     string += hover_req(file_path, 7, 40)  # multi-lin variable
     string += hover_req(file_path, 8, 7)  # function with if conditional
     string += hover_req(file_path, 9, 7)  # multiline function with if conditional
+    string += hover_req(file_path, 10, 15)  # defined without ()
     file_path = root_dir / "preproc_keywords.F90"
     string += hover_req(file_path, 6, 2)  # ignores PP across Fortran line continuations
     config = str(root_dir / ".pp_conf.json")
@@ -40,6 +41,7 @@ def check_return(result_array, checks):
         "#define varVar 55",
         "#define ewrite if (priority <= 3) write((priority), format)",
         "#define ewrite2 if (priority <= 3) write((priority), format)",
+        "#define SUCCESS .true.",
         "REAL, CONTIGUOUS, POINTER, DIMENSION(:)",
     )
     assert len(ref_results) == len(results) - 1
diff --git a/test/test_source/pp/include/petscerror.h b/test/test_source/pp/include/petscerror.h
index b1b500dd..bce29a4f 100644
--- a/test/test_source/pp/include/petscerror.h
+++ b/test/test_source/pp/include/petscerror.h
@@ -4,4 +4,9 @@
 #define PETSC_ERR_MEM              55
 #define PETSC_ERR_INT_OVERFLOW     84
 #define PETSC_ERR_FLOP_COUNT       90
+
+#if defined PETSC_ERR_MEM || defined PETSC_ERR_INT_OVERFLOW
+#define SUCCESS .true.
+#endif
+
 #endif
diff --git a/test/test_source/pp/preproc.F90 b/test/test_source/pp/preproc.F90
index 8da59d9c..5ed849c1 100644
--- a/test/test_source/pp/preproc.F90
+++ b/test/test_source/pp/preproc.F90
@@ -8,6 +8,7 @@ program preprocessor
     print*, PETSC_ERR_INT_OVERFLOW, varVar
     ewrite(1,*) 'Assemble EP P1 matrix and rhs sytem'
     ewrite2(1,*) 'Assemble EP P1 matrix and rhs sytem'
+    print*, SUCCESS
 
 #endif
 end program preprocessor
\ No newline at end of file