diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index 3a2b636d948c55d6477cedc796e0bc35a257286a..f070218eca1130d5a2b8f3788ce2f2018eea22af 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -18080,6 +18080,12 @@ aarch64_validate_mcpu (const char *str, const struct processor **res,
       case AARCH_PARSE_INVALID_ARG:
 	error ("unknown value %qs for %<-mcpu%>", str);
 	aarch64_print_hint_for_core (str);
+	/* A common user error is confusing -march and -mcpu.
+	   If the -mcpu string matches a known architecture then suggest
+	   -march=.  */
+	parse_res = aarch64_parse_arch (str, res, isa_flags, &invalid_extension);
+	if (parse_res == AARCH_PARSE_OK)
+	  inform (input_location, "did you mean %<-march=%s%>?", str);
 	break;
       case AARCH_PARSE_INVALID_FEATURE:
 	error ("invalid feature modifier %qs in %<-mcpu=%s%>",
diff --git a/gcc/testsuite/gcc.target/aarch64/spellcheck_11.c b/gcc/testsuite/gcc.target/aarch64/spellcheck_11.c
new file mode 100644
index 0000000000000000000000000000000000000000..a278328cabc486c5ff1304139b0b4cda72ebe4f8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/spellcheck_11.c
@@ -0,0 +1,13 @@
+/* { dg-do compile } */
+/* { dg-skip-if "" { *-*-* } { "-march=*" } { "" } } */
+/* { dg-skip-if "" { *-*-* } { "-mcpu=*" } { "" } } */
+/* { dg-options "-mcpu=armv8.2-a+dotprod" } */
+
+void
+foo ()
+{
+}
+
+/* { dg-error "unknown value .armv8.2-a\\+dotprod. for .-mcpu."  "" { target *-*-* } 0 } */
+/* { dg-message "valid arguments are: \[^\n\r]*"  "" { target *-*-* } 0 } */
+/* { dg-message "did you mean .-march=armv8.2-a\\+dotprod.?"  "" { target *-*-* } 0 } */