diff --git a/gcc/fortran/ChangeLog.omp b/gcc/fortran/ChangeLog.omp
index 2dd82a70cb71..09c2bb855c88 100644
--- a/gcc/fortran/ChangeLog.omp
+++ b/gcc/fortran/ChangeLog.omp
@@ -1,3 +1,10 @@
+2021-02-24  Tobias Burnus  <tobias@codesourcery.com>
+
+	Backport from mainline
+
+	* openmp.c (resolve_omp_clauses): Explicitly diagnose
+	substrings as not permitted.
+
 2021-02-24  Julian Brown  <julian@codesourcery.com>
 
 	Backport from mainline
diff --git a/gcc/fortran/openmp.c b/gcc/fortran/openmp.c
index 61a340d7f396..a7592f0545d9 100644
--- a/gcc/fortran/openmp.c
+++ b/gcc/fortran/openmp.c
@@ -4978,7 +4978,13 @@ resolve_omp_clauses (gfc_code *code, gfc_omp_clauses *omp_clauses,
 		    || (n->expr
 			&& (!resolved || n->expr->expr_type != EXPR_VARIABLE)))
 		  {
-		    if (!resolved
+		    if (array_ref
+			&& (array_ref->type == REF_SUBSTRING
+			    || (array_ref->next
+				&& array_ref->next->type == REF_SUBSTRING)))
+		      gfc_error ("Unexpected substring reference in %s clause "
+				 "at %L", name, &n->where);
+		    else if (!resolved
 			|| n->expr->expr_type != EXPR_VARIABLE
 			|| array_ref->next
 			|| array_ref->type != REF_ARRAY)
diff --git a/gcc/testsuite/ChangeLog.omp b/gcc/testsuite/ChangeLog.omp
index e04a4ee3ebff..d012e9e75b4e 100644
--- a/gcc/testsuite/ChangeLog.omp
+++ b/gcc/testsuite/ChangeLog.omp
@@ -1,3 +1,10 @@
+2021-02-24  Tobias Burnus  <tobias@codesourcery.com>
+
+	Backport from mainline
+
+	* gfortran.dg/goacc/substring.f90: New test.
+	* gfortran.dg/gomp/substring.f90: New test.
+
 2021-02-24  Julian Brown  <julian@codesourcery.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/gfortran.dg/goacc/substring.f90 b/gcc/testsuite/gfortran.dg/goacc/substring.f90
new file mode 100644
index 000000000000..25031daddf33
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/goacc/substring.f90
@@ -0,0 +1,27 @@
+implicit none
+character(len=10) :: str1, str2(5,5)
+
+type t
+  character(len=10) :: str1, str2(5,5)
+end type t
+type(t) :: v
+
+!$acc enter data copyin(v%str1)       ! OK
+!$acc enter data copyin(v%str2)       ! OK
+!$acc enter data copyin(v%str2(1,2))  ! OK
+!$acc enter data copyin(str1)         ! OK
+!$acc enter data copyin(str2)         ! OK
+!$acc enter data copyin(str2(1,2))    ! OK
+
+!$acc enter data copyin(v%str1(2:5))       ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc enter data copyin(v%str2(1,2)(2:4))  ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc enter data copyin(str1(2:5))         ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc enter data copyin(str2(1,2)(2:4))    ! { dg-error "Unexpected substring reference in MAP clause" }
+
+!$acc parallel
+!$acc update host(v%str1(2:5))             ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc update host(v%str2(1,2)(2:4))        ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc update host(str1(2:5))               ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc update host(str2(1,2)(2:4))          ! { dg-error "Unexpected substring reference in MAP clause" }
+!$acc end parallel
+end
diff --git a/gcc/testsuite/gfortran.dg/gomp/substring.f90 b/gcc/testsuite/gfortran.dg/gomp/substring.f90
new file mode 100644
index 000000000000..23d7fb7e48ab
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/gomp/substring.f90
@@ -0,0 +1,22 @@
+implicit none
+character(len=10) :: str1, str2(5,5)
+
+type t
+  character(len=10) :: str1, str2(5,5)
+end type t
+type(t) :: v
+
+!$omp target enter data map(to: str1)      ! OK
+!$omp target enter data map(to: str2)      ! OK
+!$omp target enter data map(to: str2(2,5)) ! OK
+
+!$omp target enter data map(to: str1(2,5))         ! { dg-error "Syntax error in OpenMP variable list" }
+!$omp target enter data map(to: str2(1,2)(2:4))    ! { dg-error "Unexpected substring reference in MAP clause" }
+
+!$omp target enter data map(to: v%str1)       ! OK
+!$omp target enter data map(to: v%str2)       ! OK
+!$omp target enter data map(to: v%str2(1,2))  ! OK
+
+!$omp target enter data map(to: v%str1(2:5))       ! { dg-error "Unexpected substring reference in MAP clause" }
+!$omp target enter data map(to: v%str2(1,2)(2:4))  ! { dg-error "Unexpected substring reference in MAP clause" }
+end
