diff --git a/flang/lib/Optimizer/OpenMP/MapInfoFinalization.cpp b/flang/lib/Optimizer/OpenMP/MapInfoFinalization.cpp
index 3fe133d63d24d..a60960e739d24 100644
--- a/flang/lib/Optimizer/OpenMP/MapInfoFinalization.cpp
+++ b/flang/lib/Optimizer/OpenMP/MapInfoFinalization.cpp
@@ -1143,7 +1143,8 @@ class MapInfoFinalizationPass
           newMemberIndices.emplace_back(path);
 
         op.setMembersIndexAttr(builder.create2DI64ArrayAttr(newMemberIndices));
-        op.setPartialMap(true);
+        // Set to partial map only if there is no user-defined mapper.
+        op.setPartialMap(op.getMapperIdAttr() == nullptr);
 
         return mlir::WalkResult::advance();
       });
diff --git a/flang/test/Transforms/omp-map-info-finalization-implicit-field.fir b/flang/test/Transforms/omp-map-info-finalization-implicit-field.fir
index 632525b4b43c9..d3e8125d2ee3d 100644
--- a/flang/test/Transforms/omp-map-info-finalization-implicit-field.fir
+++ b/flang/test/Transforms/omp-map-info-finalization-implicit-field.fir
@@ -15,13 +15,24 @@ fir.global internal @_QFEdst_record : !record_t {
   fir.has_value %0 : !record_t
 }
 
+omp.declare_mapper @record_mapper : !record_t {
+^bb0(%arg0: !fir.ref<!record_t>):
+  %0 = omp.map.info var_ptr(%arg0: !fir.ref<!record_t>, !record_t) map_clauses(implicit, tofrom) capture(ByRef) -> !fir.ref<!record_t>
+  omp.declare_mapper.info map_entries(%0: !fir.ref<!record_t>)
+}
+
 func.func @_QQmain() {
   %6 = fir.address_of(@_QFEdst_record) : !fir.ref<!record_t>
   %7:2 = hlfir.declare %6 {uniq_name = "_QFEdst_record"} : (!fir.ref<!record_t>) -> (!fir.ref<!record_t>, !fir.ref<!record_t>)
   %16 = omp.map.info var_ptr(%7#1 : !fir.ref<!record_t>, !record_t) map_clauses(implicit, tofrom) capture(ByRef) -> !fir.ref<!record_t> {name = "dst_record"}
-  omp.target map_entries(%16 -> %arg0 : !fir.ref<!record_t>) {
+  %17 = omp.map.info var_ptr(%7#1 : !fir.ref<!record_t>, !record_t) map_clauses(implicit, tofrom) capture(ByRef) mapper(@record_mapper) -> !fir.ref<!record_t> {name = "dst_record_with_mapper"}
+  omp.target map_entries(%16 -> %arg0, %17 -> %arg1 : !fir.ref<!record_t>, !fir.ref<!record_t>) {
     %20:2 = hlfir.declare %arg0 {uniq_name = "_QFEdst_record"} : (!fir.ref<!record_t>) -> (!fir.ref<!record_t>, !fir.ref<!record_t>)
+    %21:2 = hlfir.declare %arg1 {uniq_name = "_QFEdst_record"} : (!fir.ref<!record_t>) -> (!fir.ref<!record_t>, !fir.ref<!record_t>)
+
     %23 = hlfir.designate %20#0{"to_implicitly_map"}   {fortran_attrs = #fir.var_attrs<allocatable>} : (!fir.ref<!record_t>) -> !fir.ref<!fir.box<!fir.heap<!fir.array<?xf32>>>>
+
+    %24 = hlfir.designate %21#0{"to_implicitly_map"}   {fortran_attrs = #fir.var_attrs<allocatable>} : (!fir.ref<!record_t>) -> !fir.ref<!fir.box<!fir.heap<!fir.array<?xf32>>>>
     omp.terminator
   }
   return
@@ -56,6 +67,19 @@ func.func @_QQmain() {
 // CHECK-SAME: [1], [1, 0] : {{.*}}) -> {{.*}}> {name =
 // CHECK-SAME: "dst_record", partial_map = true}
 
+// Verify map ops when using a mapper:
+// Implicit field mapping is the same as for the non-mapper case.
+// CHECK: omp.map.info
+// CHECK: omp.map.info
+
+// Verify that partial-map is not set if the map info op uses a user-defined (or
+// compiler-emitted) mapper.
+// CHECK: %[[RECORD_MAP_MAPPER:.*]] = omp.map.info var_ptr(
+// CHECK-SAME: %[[RECORD_DECL]]#1 : {{.*}}) map_clauses(
+// CHECK-SAME: implicit, tofrom) capture(ByRef) mapper(@record_mapper) 
+// CHECK-SAME: members(%{{.*}}, %{{.*}} : [1], [1, 0] : {{.*}}) -> {{.*}}> {name =
+// CHECK-SAME: "dst_record_with_mapper"}
+
 // CHECK: omp.target map_entries(
 // CHECK-SAME: %[[RECORD_MAP]] -> %{{[^[:space:]]+}},
 // CHECK-SAME: %[[FIELD_MAP]] -> %{{[^[:space:]]+}},
diff --git a/offload/test/offloading/fortran/default-mapper-nested-derived-type.f90 b/offload/test/offloading/fortran/default-mapper-nested-derived-type.f90
new file mode 100644
index 0000000000000..5d69fa072fd63
--- /dev/null
+++ b/offload/test/offloading/fortran/default-mapper-nested-derived-type.f90
@@ -0,0 +1,34 @@
+! Regression test for default mappers emitted for nested derived types. Some
+! optimization passes and instrumentation callbacks cause crashes in emitted
+! mappers and this test guards against such crashes.
+
+! REQUIRES: flang, amdgpu
+
+! RUN: %libomptarget-compile-fortran-generic
+! RUN: env LIBOMPTARGET_INFO=16 %libomptarget-run-generic 2>&1 | %fcheck-generic
+
+program test_omp_target_map_bug_v5
+  implicit none
+  type nested_type
+    real, allocatable :: alloc_field(:)
+  end type nested_type
+
+  type nesting_type
+    integer :: int_field
+    type(nested_type) :: derived_field
+  end type nesting_type
+
+  type(nesting_type) :: config
+
+  allocate(config%derived_field%alloc_field(1))
+
+  !$OMP TARGET ENTER DATA MAP(TO:config, config%derived_field%alloc_field)
+
+  !$OMP TARGET
+  config%derived_field%alloc_field(1) = 1.0
+  !$OMP END TARGET
+
+  deallocate(config%derived_field%alloc_field)
+end program test_omp_target_map_bug_v5
+
+! CHECK:  "PluginInterface" device {{[0-9]+}} info: Launching kernel {{.*}}