diff --git a/gcc/common/config/i386/i386-common.c b/gcc/common/config/i386/i386-common.c
index eea8af12f48..b89183b830e 100644
--- a/gcc/common/config/i386/i386-common.c
+++ b/gcc/common/config/i386/i386-common.c
@@ -2051,7 +2051,7 @@ const pta processor_alias_table[] =
 };
 
 /* NB: processor_alias_table stops at the "generic" entry.  */
-unsigned int const pta_size = ARRAY_SIZE (processor_alias_table) - 6;
+unsigned int const pta_size = ARRAY_SIZE (processor_alias_table) - 7;
 unsigned int const num_arch_names = ARRAY_SIZE (processor_alias_table);
 
 /* Provide valid option values for -march and -mtune options.  */
diff --git a/gcc/config/i386/i386-options.c b/gcc/config/i386/i386-options.c
index b653527d266..88d5e717f26 100644
--- a/gcc/config/i386/i386-options.c
+++ b/gcc/config/i386/i386-options.c
@@ -2042,6 +2042,9 @@ ix86_option_override_internal (bool main_args_p,
     sorry ("%i-bit mode not compiled in",
 	   (opts->x_ix86_isa_flags & OPTION_MASK_ISA_64BIT) ? 64 : 32);
 
+  /* Last processor_alias_table must point to "generic" entry.  */
+  gcc_checking_assert (strcmp (processor_alias_table[pta_size - 1].name,
+			       "generic") == 0);
   for (i = 0; i < pta_size; i++)
     if (! strcmp (opts->x_ix86_arch_string, processor_alias_table[i].name))
       {
diff --git a/gcc/testsuite/gcc.target/i386/pr99753.c b/gcc/testsuite/gcc.target/i386/pr99753.c
new file mode 100644
index 00000000000..3def1fd7481
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr99753.c
@@ -0,0 +1,5 @@
+/* PR target/99753 */
+
+/* { dg-do compile } */
+/* { dg-options "-march=amd -m32" } */
+/* { dg-error "bad value .'amd'. for '-march=' switch"  "" { target *-*-* } 0 } */