diff --git a/openmp/runtime/src/kmp_runtime.cpp b/openmp/runtime/src/kmp_runtime.cpp
--- a/openmp/runtime/src/kmp_runtime.cpp
+++ b/openmp/runtime/src/kmp_runtime.cpp
@@ -1153,6 +1153,9 @@
   // Reset for next parallel region
   this_thr->th.th_set_proc_bind = proc_bind_default;
 
+  // Reset num_threads for next parallel region
+  this_thr->th.th_set_nproc = 0;
+
 #if OMPT_SUPPORT
   ompt_data_t ompt_parallel_data = ompt_data_none;
   void *codeptr = OMPT_LOAD_RETURN_ADDRESS(global_tid);
diff --git a/openmp/runtime/test/parallel/bug63197.c b/openmp/runtime/test/parallel/bug63197.c
new file mode 100644
--- /dev/null
+++ b/openmp/runtime/test/parallel/bug63197.c
@@ -0,0 +1,17 @@
+// RUN: %libomp-compile-and-run | FileCheck %s
+
+#include <omp.h>
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+#pragma omp parallel num_threads(3) if (false)
+#pragma omp single
+  { printf("BBB %2d\n", omp_get_num_threads()); }
+
+#pragma omp parallel
+#pragma omp single
+  { printf("CCC %2d\n", omp_get_num_threads()); }
+  return 0;
+}
+
+// CHECK-NOT: CCC  3