diff --git a/toolchain/check/handle_loop_statement.cpp b/toolchain/check/handle_loop_statement.cpp
index 0f60a1dad231..52afbb8ed775 100644
--- a/toolchain/check/handle_loop_statement.cpp
+++ b/toolchain/check/handle_loop_statement.cpp
@@ -224,11 +224,15 @@ auto HandleParseNode(Context& context, Parse::ForHeaderId node_id) -> bool {
       context, node_id,
       {.type_id = GetPointerType(context, cursor_type_inst_id),
        .lvalue_id = cursor_var_id});
+  // A range that implements neither fails both lookups; reporting the second
+  // would say the same thing about the same expression a second time.
+  // TODO: We should only perform the impl lookup once.
   auto element_id =
       BuildBinaryOperator(context, node_id,
                           {.interface_name = CoreIdentifier::Iterate,
                            .op_name = CoreIdentifier::Next},
-                          range_id, cursor_addr_id);
+                          range_id, cursor_addr_id,
+                          /*diagnose=*/cursor_id != SemIR::ErrorInst::InstId);
   // We need to convert away from an initializing expression in order to call
   // `HasValue` and then separately pattern-match against the element.
   // TODO: Instead, form a `.Some(pattern_id)` pattern and pattern-match against
diff --git a/toolchain/check/testdata/for/basic.carbon b/toolchain/check/testdata/for/basic.carbon
index 7fd3d7623a81..0f61780cb57e 100644
--- a/toolchain/check/testdata/for/basic.carbon
+++ b/toolchain/check/testdata/for/basic.carbon
@@ -15,11 +15,7 @@
 library "[[@TEST_NAME]]";
 
 fn Run() {
-  // TODO: These diagnostics could be better. If nothing else, we should only diagnose once.
-  // CHECK:STDERR: fail_not_range.carbon:[[@LINE+8]]:7: error: cannot access member of interface `Core.Iterate` in type `{}` that does not implement that interface [MissingImplInMemberAccess]
-  // CHECK:STDERR:   for (unused c: {} in {}) {
-  // CHECK:STDERR:       ^~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR:
+  // TODO: These diagnostics could be better.
   // CHECK:STDERR: fail_not_range.carbon:[[@LINE+4]]:7: error: cannot access member of interface `Core.Iterate` in type `{}` that does not implement that interface [MissingImplInMemberAccess]
   // CHECK:STDERR:   for (unused c: {} in {}) {
   // CHECK:STDERR:       ^~~~~~~~~~~~~~~~~~~~
diff --git a/toolchain/check/testdata/interop/cpp/range_for.carbon b/toolchain/check/testdata/interop/cpp/range_for.carbon
index 4fa7306ef472..00a34b73f83d 100644
--- a/toolchain/check/testdata/interop/cpp/range_for.carbon
+++ b/toolchain/check/testdata/interop/cpp/range_for.carbon
@@ -442,10 +442,6 @@ fn TestRangeFor(var m: Cpp.DiffMutableADL.MutableRange) {
   var sum: Cpp.DiffMutableADL.ValueType = Cpp.DiffMutableADL.ValueType.ValueType();
 
   //@dump-sem-ir-begin
-  // CHECK:STDERR: fail_todo_adl_returns_different_types_mutable.carbon:[[@LINE+8]]:7: error: cannot access member of interface `Core.Iterate` in type `Cpp.DiffMutableADL.MutableRange` that does not implement that interface [MissingImplInMemberAccess]
-  // CHECK:STDERR:   for (i: Cpp.DiffMutableADL.ValueType in m) {
-  // CHECK:STDERR:       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-  // CHECK:STDERR:
   // CHECK:STDERR: fail_todo_adl_returns_different_types_mutable.carbon:[[@LINE+4]]:7: error: cannot access member of interface `Core.Iterate` in type `Cpp.DiffMutableADL.MutableRange` that does not implement that interface [MissingImplInMemberAccess]
   // CHECK:STDERR:   for (i: Cpp.DiffMutableADL.ValueType in m) {
   // CHECK:STDERR:       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -4085,16 +4081,16 @@ fn TestDriver(var no_begin_end: Cpp.NoBeginEnd,
 // CHECK:STDOUT:   br !for.next
 // CHECK:STDOUT:
 // CHECK:STDOUT: !for.next:
-// CHECK:STDOUT:   %addr.loc98: <error> = addr_of <error> [concrete = <error>]
+// CHECK:STDOUT:   %addr.loc94: <error> = addr_of <error> [concrete = <error>]
 // CHECK:STDOUT:   %HasValue.ref: <error> = name_ref HasValue, <error> [concrete = <error>]
 // CHECK:STDOUT:   if <error> br !for.body else br !for.done
 // CHECK:STDOUT:
 // CHECK:STDOUT: !for.body:
 // CHECK:STDOUT:   %Get.ref: <error> = name_ref Get, <error> [concrete = <error>]
-// CHECK:STDOUT:   %.loc98: type = splice_block %ValueType.ref.loc98 [concrete = constants.%ValueType] {
-// CHECK:STDOUT:     %Cpp.ref.loc98: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
-// CHECK:STDOUT:     %DiffMutableADL.ref.loc98: <namespace> = name_ref DiffMutableADL, imports.%DiffMutableADL [concrete = imports.%DiffMutableADL]
-// CHECK:STDOUT:     %ValueType.ref.loc98: type = name_ref ValueType, imports.%ValueType.decl [concrete = constants.%ValueType]
+// CHECK:STDOUT:   %.loc94: type = splice_block %ValueType.ref.loc94 [concrete = constants.%ValueType] {
+// CHECK:STDOUT:     %Cpp.ref.loc94: <namespace> = name_ref Cpp, imports.%Cpp [concrete = imports.%Cpp]
+// CHECK:STDOUT:     %DiffMutableADL.ref.loc94: <namespace> = name_ref DiffMutableADL, imports.%DiffMutableADL [concrete = imports.%DiffMutableADL]
+// CHECK:STDOUT:     %ValueType.ref.loc94: type = name_ref ValueType, imports.%ValueType.decl [concrete = constants.%ValueType]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %i: %ValueType = wrapper_binding i, <error> [concrete = <error>]
 // CHECK:STDOUT:   %sum.ref: ref %ValueType = name_ref sum, %sum