diff --git a/src/dynarec/dynarec_native_pass.c b/src/dynarec/dynarec_native_pass.c
index e13a316f22..87ea386f6a 100644
--- a/src/dynarec/dynarec_native_pass.c
+++ b/src/dynarec/dynarec_native_pass.c
@@ -275,7 +275,7 @@ uintptr_t native_pass(dynarec_native_t* dyn, uintptr_t addr, int alternate, int
         rex.is67 = 0;
         rex.isf0 = 0;
         rex.rep = 0;
-        uint8_t prefix = x64_prefix_kind[pk];
+        uint8_t prefix = x64_prefix_kind_table[pk];
         while(prefix && (prefix!=X64_PREFIX_REX || !is32bits)) {
             switch (prefix) {
                 case X64_PREFIX_LOCK: rex.isf0 = 1; rex.rex = 0; break;
@@ -290,7 +290,7 @@ uintptr_t native_pass(dynarec_native_t* dyn, uintptr_t addr, int alternate, int
             }
             ++addr;
             pk = PK(0);
-            prefix = x64_prefix_kind[pk];
+            prefix = x64_prefix_kind_table[pk];
         }
         if(rex.isf0) {
             if(rex.is66 && !rex.w)
diff --git a/src/emu/x64run.c b/src/emu/x64run.c
index f32e0ab5d1..0522eed6d5 100644
--- a/src/emu/x64run.c
+++ b/src/emu/x64run.c
@@ -108,26 +108,21 @@ int Run(x64emu_t *emu, int step)
         rex.is67 = 0;
         rex.isf0 = 0;
         rex.rep = 0;
-        while((opcode==0xF2) || (opcode==0xF3) || (opcode==0xF0)
-            || (opcode==0x3E) || (opcode==0x26) || (opcode==0x2e) || (opcode==0x36) 
-            || (opcode==0x64) || (opcode==0x65) || (opcode==0x66) || (opcode==0x67)
-            || (!is32bits && (opcode>=0x40 && opcode<=0x4f))) {
-            switch (opcode) {
-                case 0xF0: rex.isf0 = 1; rex.rex = 0; break;
-                case 0xF2: rex.rep = 1; rex.rex = 0; break;
-                case 0xF3: rex.rep = 2; rex.rex = 0; break;
-                case 0x26: /* ES: */
-                case 0x2E: /* CS: */
-                case 0x36: /* SS; */
-                case 0x3E: /* DS; */ 
-                           rex.seg =   0; rex.rex = 0; break;
-                case 0x64: rex.seg = _FS; rex.rex = 0; break;
-                case 0x65: rex.seg = _GS; rex.rex = 0; break;
-                case 0x66: rex.is66 = 1; rex.rex = 0; break;
-                case 0x67: rex.is67 = 1; rex.rex = 0; break;
-                case 0x40 ... 0x4F: rex.rex = opcode; break;
+        uint8_t prefix = x64_prefix_kind_table[opcode];
+        while(prefix && (prefix!=X64_PREFIX_REX || !is32bits)) {
+            switch (prefix) {
+                case X64_PREFIX_LOCK: rex.isf0 = 1; rex.rex = 0; break;
+                case X64_PREFIX_REP_F2: rex.rep = 1; rex.rex = 0; break;
+                case X64_PREFIX_REP_F3: rex.rep = 2; rex.rex = 0; break;
+                case X64_PREFIX_SEG0: rex.seg = 0; rex.rex = 0; break;
+                case X64_PREFIX_FS: rex.seg = _FS; rex.rex = 0; break;
+                case X64_PREFIX_GS: rex.seg = _GS; rex.rex = 0; break;
+                case X64_PREFIX_66: rex.is66 = 1; rex.rex = 0; break;
+                case X64_PREFIX_67: rex.is67 = 1; rex.rex = 0; break;
+                case X64_PREFIX_REX: rex.rex = opcode; break;
             }
             opcode = F8;
+            prefix = x64_prefix_kind_table[opcode];
         }
 
         if(rex.seg)
diff --git a/src/emu/x64run_private.c b/src/emu/x64run_private.c
index cc31ff2e36..a37a6c8f2a 100644
--- a/src/emu/x64run_private.c
+++ b/src/emu/x64run_private.c
@@ -30,6 +30,36 @@
 #define from_ptrv(A) ((void*)(uintptr_t)(A))
 #endif
 
+const uint8_t x64_prefix_kind_table[256] = {
+    [0x26] = X64_PREFIX_SEG0,
+    [0x2e] = X64_PREFIX_SEG0,
+    [0x36] = X64_PREFIX_SEG0,
+    [0x3e] = X64_PREFIX_SEG0,
+    [0x40] = X64_PREFIX_REX,
+    [0x41] = X64_PREFIX_REX,
+    [0x42] = X64_PREFIX_REX,
+    [0x43] = X64_PREFIX_REX,
+    [0x44] = X64_PREFIX_REX,
+    [0x45] = X64_PREFIX_REX,
+    [0x46] = X64_PREFIX_REX,
+    [0x47] = X64_PREFIX_REX,
+    [0x48] = X64_PREFIX_REX,
+    [0x49] = X64_PREFIX_REX,
+    [0x4a] = X64_PREFIX_REX,
+    [0x4b] = X64_PREFIX_REX,
+    [0x4c] = X64_PREFIX_REX,
+    [0x4d] = X64_PREFIX_REX,
+    [0x4e] = X64_PREFIX_REX,
+    [0x4f] = X64_PREFIX_REX,
+    [0x64] = X64_PREFIX_FS,
+    [0x65] = X64_PREFIX_GS,
+    [0x66] = X64_PREFIX_66,
+    [0x67] = X64_PREFIX_67,
+    [0xf0] = X64_PREFIX_LOCK,
+    [0xf2] = X64_PREFIX_REP_F2,
+    [0xf3] = X64_PREFIX_REP_F3,
+};
+
 
 #ifdef HAVE_TRACE
 #define PK(a)     (*(uint8_t*)(ip+a))
diff --git a/src/emu/x64run_private.h b/src/emu/x64run_private.h
index bc920b6ec5..f1b99c3787 100644
--- a/src/emu/x64run_private.h
+++ b/src/emu/x64run_private.h
@@ -8,6 +8,20 @@
 #include "symbolfuncs.h"
 #include "x64emu.h"
 
+enum {
+    X64_PREFIX_LOCK = 1,
+    X64_PREFIX_REP_F2,
+    X64_PREFIX_REP_F3,
+    X64_PREFIX_SEG0,
+    X64_PREFIX_FS,
+    X64_PREFIX_GS,
+    X64_PREFIX_66,
+    X64_PREFIX_67,
+    X64_PREFIX_REX,
+};
+
+extern const uint8_t x64_prefix_kind_table[256];
+
 typedef struct rex_s {
     union {
         uint8_t rex;