diff --git a/gcc/fortran/ChangeLog b/gcc/fortran/ChangeLog
index a396418118d..6f2ba754726 100644
--- a/gcc/fortran/ChangeLog
+++ b/gcc/fortran/ChangeLog
@@ -1,3 +1,9 @@
+2019-09-13  Steven G. Kargl  <kargl@gcc.gnu.org>
+
+	PR fortran/91566
+	* simplify.c (gfc_simplify_merge): Need to simplify expression
+	after insertation of parenthesis.
+
 2019-09-13  Bernd Edlinger  <bernd.edlinger@hotmail.de>
 
 	PR fortran/91716
diff --git a/gcc/fortran/simplify.c b/gcc/fortran/simplify.c
index 023eedb749c..3d2fc0d956f 100644
--- a/gcc/fortran/simplify.c
+++ b/gcc/fortran/simplify.c
@@ -4780,8 +4780,13 @@ gfc_simplify_merge (gfc_expr *tsource, gfc_expr *fsource, gfc_expr *mask)
   gfc_constructor *tsource_ctor, *fsource_ctor, *mask_ctor;
 
   if (mask->expr_type == EXPR_CONSTANT)
-    return gfc_get_parentheses (gfc_copy_expr (mask->value.logical
-					       ? tsource : fsource));
+    {
+      result = gfc_copy_expr (mask->value.logical ? tsource : fsource);
+      /* Parenthesis is needed to get lower bounds of 1.  */
+      result = gfc_get_parentheses (result);
+      gfc_simplify_expr (result, 1);
+      return result;
+    }
 
   if (!mask->rank || !is_constant_array_expr (mask)
       || !is_constant_array_expr (tsource) || !is_constant_array_expr (fsource))
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 62766c21556..8bb7e7af3de 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2019-09-13  Steven G. Kargl  <kargl@gcc.gnu.org>
+
+	PR fortran/91566
+	* gfortran.dg/pr91566.f90:
+
 2019-09-13  Bernd Edlinger  <bernd.edlinger@hotmail.de>
 
 	PR fortran/91716
diff --git a/gcc/testsuite/gfortran.dg/pr91566.f90 b/gcc/testsuite/gfortran.dg/pr91566.f90
new file mode 100644
index 00000000000..fdb35b44199
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr91566.f90
@@ -0,0 +1,14 @@
+! { dg-do compile }
+! Code contributed by Gerhard Steinmetz
+program p
+   call q
+   call r
+end program p
+
+subroutine q
+   print *, -merge([3,4], 0, [.false.,.true.])
+end
+
+subroutine r
+   print *, 2 + merge([3,4], 0, [.false.,.true.])
+end