diff --git a/gcc/testsuite/c-c++-common/gomp/pr100450.c b/gcc/testsuite/c-c++-common/gomp/pr100450.c
new file mode 100644
index 00000000000..a6d2a2829ff
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/gomp/pr100450.c
@@ -0,0 +1,20 @@
+/* PR c/100450 */
+/* { dg-do compile } */
+/* { dg-options "-fopenmp -save-temps -Wunknown-pragmas" } */
+
+#define TEST(T) { \
+     {T} \
+}
+#define CLAUSES reduction(+:red)
+#define PARALLEL_FOR(X) TEST({ \
+_Pragma("omp for CLAUSES") \
+X \
+})
+
+void foo()
+{
+  int red = 0;
+  int A[3] = {};
+  #pragma omp parallel shared(red)
+  PARALLEL_FOR( for(int i=0; i < 3; i++) red += A[i]; )
+}
diff --git a/libcpp/lex.c b/libcpp/lex.c
index 9662f1b8ca2..b7ce85a0331 100644
--- a/libcpp/lex.c
+++ b/libcpp/lex.c
@@ -3719,6 +3719,7 @@ cpp_avoid_paste (cpp_reader *pfile, const cpp_token *token1,
     case CPP_DEREF:	return c == '*';
     case CPP_DOT:	return c == '.' || c == '%' || b == CPP_NUMBER;
     case CPP_HASH:	return c == '#' || c == '%'; /* Digraph form.  */
+    case CPP_PRAGMA:
     case CPP_NAME:	return ((b == CPP_NUMBER
 				 && name_p (pfile, &token2->val.str))
 				|| b == CPP_NAME