diff --git a/ggml/src/ggml-amx/ggml-amx.cpp b/ggml/src/ggml-amx/ggml-amx.cpp
index 144dc9d8a..2db0b720a 100644
--- a/ggml/src/ggml-amx/ggml-amx.cpp
+++ b/ggml/src/ggml-amx/ggml-amx.cpp
@@ -433,4 +433,8 @@ void ggml_backend_amx_set_n_threads(ggml_backend_t backend_amx, int n_threads) {
     GGML_UNUSED(n_threads);
 }
 
+ggml_backend_reg_t ggml_backend_amx_reg(void) {
+    return nullptr;
+}
+
 #endif
diff --git a/ggml/src/ggml-amx/mmq.cpp b/ggml/src/ggml-amx/mmq.cpp
index 239d15121..529bee25b 100644
--- a/ggml/src/ggml-amx/mmq.cpp
+++ b/ggml/src/ggml-amx/mmq.cpp
@@ -496,19 +496,20 @@ inline void from_float(const float * x, char * vy, int64_t k);
 
 template <>
 inline void from_float<block_q8_0>(const float * x, char * vy, int64_t k) {
-    quantize_row_q8_0(x, vy, k);
+    // FIXME: using unoptimized reference impl until moved to CPU backend
+    quantize_row_q8_0_ref(x, (block_q8_0 *)vy, k);
 }
 
 template <>
 inline void from_float<block_q8_1>(const float * x, char * vy, int64_t k) {
-    quantize_row_q8_1(x, vy, k);
+    quantize_row_q8_1_ref(x, (block_q8_1 *)vy, k);
 }
 
 template <>
 inline void from_float<block_q8_K>(const float * x, char * vy, int64_t k) {
 #if 1
     // TODO: this is reference impl!
-    quantize_row_q8_K(x, vy, k);
+    quantize_row_q8_K_ref(x, (block_q8_K *)vy, k);
 #else
     quantize_row_q8_K_vnni(x, vy, k);
 #endif
diff --git a/ggml/src/ggml-backend-reg.cpp b/ggml/src/ggml-backend-reg.cpp
index 6bd537d96..63e9d8201 100644
--- a/ggml/src/ggml-backend-reg.cpp
+++ b/ggml/src/ggml-backend-reg.cpp
@@ -31,10 +31,6 @@
 #include "ggml-rpc.h"
 #endif
 
-#ifndef __AMX_INT8__
-#undef GGML_USE_AMX
-#endif
-
 #ifdef GGML_USE_AMX
 #  include "ggml-amx.h"
 #endif
@@ -84,6 +80,10 @@ struct ggml_backend_registry {
     }
 
     void register_backend(ggml_backend_reg_t reg) {
+        if (!reg) {
+            return;
+        }
+
 #ifndef NDEBUG
         GGML_LOG_DEBUG("%s: registered backend %s (%zu devices)\n",
             __func__, ggml_backend_reg_name(reg), ggml_backend_reg_dev_count(reg));