diff --git a/gcc/fortran/resolve.c b/gcc/fortran/resolve.c
index c02bbed87395776baf68c9adcc89028dcd45f4d4..747516fbc1d730c9116e1f06ca717aed512f17d2 100644
--- a/gcc/fortran/resolve.c
+++ b/gcc/fortran/resolve.c
@@ -11940,6 +11940,12 @@ start:
 
 	  if (resolve_ordinary_assign (code, ns))
 	    {
+	      if (omp_workshare_flag)
+		{
+		  gfc_error ("Expected intrinsic assignment in OMP WORKSHARE "
+			     "at %L", &code->loc);
+		  break;
+		}
 	      if (code->op == EXEC_COMPCALL)
 		goto compcall;
 	      else
diff --git a/gcc/testsuite/gfortran.dg/gomp/workshare-59.f90 b/gcc/testsuite/gfortran.dg/gomp/workshare-59.f90
new file mode 100644
index 0000000000000000000000000000000000000000..65d04c2b55d411fd7b63a1c76b47b70fa8934942
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/workshare-59.f90
@@ -0,0 +1,26 @@
+! PR fortran/100633
+
+module defined_assign
+  interface assignment(=)
+    module procedure work_assign
+  end interface
+
+  contains
+    subroutine work_assign(a,b)
+      integer, intent(out) :: a
+      logical, intent(in) :: b(:)
+    end subroutine work_assign
+end module defined_assign
+
+program omp_workshare
+  use defined_assign
+
+  integer :: a
+  logical :: l(10)
+  l = .TRUE.
+
+  !$omp workshare
+  a = l   ! { dg-error "Expected intrinsic assignment in OMP WORKSHARE" }
+  !$omp end workshare
+
+end program omp_workshare