diff --git a/src/jit/frontend/sh4/sh4_frontend.c b/src/jit/frontend/sh4/sh4_frontend.c
index 972a27aa..e5f7fcba 100644
--- a/src/jit/frontend/sh4/sh4_frontend.c
+++ b/src/jit/frontend/sh4/sh4_frontend.c
@@ -179,51 +179,51 @@ static void sh4_frontend_analyze_code(struct jit_frontend *base,
     if (def->flags & SH4_FLAG_SET_PC) {
       if (def->op == SH4_OP_BF) {
         uint32_t dest_addr = ((int8_t)instr.disp_8.disp * 2) + addr + 4;
-        block->branch_type = BRANCH_STATIC_FALSE;
+        block->branch_type = JIT_BRANCH_STATIC_FALSE;
         block->branch_addr = dest_addr;
         block->next_addr = addr + 4;
       } else if (def->op == SH4_OP_BFS) {
         uint32_t dest_addr = ((int8_t)instr.disp_8.disp * 2) + addr + 4;
-        block->branch_type = BRANCH_STATIC_FALSE;
+        block->branch_type = JIT_BRANCH_STATIC_FALSE;
         block->branch_addr = dest_addr;
         block->next_addr = addr + 4;
       } else if (def->op == SH4_OP_BT) {
         uint32_t dest_addr = ((int8_t)instr.disp_8.disp * 2) + addr + 4;
-        block->branch_type = BRANCH_STATIC_TRUE;
+        block->branch_type = JIT_BRANCH_STATIC_TRUE;
         block->branch_addr = dest_addr;
         block->next_addr = addr + 4;
       } else if (def->op == SH4_OP_BTS) {
         uint32_t dest_addr = ((int8_t)instr.disp_8.disp * 2) + addr + 4;
-        block->branch_type = BRANCH_STATIC_TRUE;
+        block->branch_type = JIT_BRANCH_STATIC_TRUE;
         block->branch_addr = dest_addr;
         block->next_addr = addr + 4;
       } else if (def->op == SH4_OP_BRA) {
         /* 12-bit displacement must be sign extended */
         int32_t disp = ((instr.disp_12.disp & 0xfff) << 20) >> 20;
         uint32_t dest_addr = (disp * 2) + addr + 4;
-        block->branch_type = BRANCH_STATIC;
+        block->branch_type = JIT_BRANCH_STATIC;
         block->branch_addr = dest_addr;
       } else if (def->op == SH4_OP_BRAF) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else if (def->op == SH4_OP_BSR) {
         /* 12-bit displacement must be sign extended */
         int32_t disp = ((instr.disp_12.disp & 0xfff) << 20) >> 20;
         uint32_t ret_addr = addr + 4;
         uint32_t dest_addr = ret_addr + disp * 2;
-        block->branch_type = BRANCH_STATIC;
+        block->branch_type = JIT_BRANCH_STATIC;
         block->branch_addr = dest_addr;
       } else if (def->op == SH4_OP_BSRF) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else if (def->op == SH4_OP_JMP) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else if (def->op == SH4_OP_JSR) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else if (def->op == SH4_OP_RTS) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else if (def->op == SH4_OP_RTE) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else if (def->op == SH4_OP_TRAPA) {
-        block->branch_type = BRANCH_DYNAMIC;
+        block->branch_type = JIT_BRANCH_DYNAMIC;
       } else {
         LOG_FATAL("unexpected branch op");
       }
diff --git a/src/jit/jit.c b/src/jit/jit.c
index a89b6693..cafddc78 100644
--- a/src/jit/jit.c
+++ b/src/jit/jit.c
@@ -139,7 +139,9 @@ static void jit_restore_edges(struct jit *jit, struct jit_block *block) {
   PROF_LEAVE();
 }
 
-static void jit_invalidate_block(struct jit *jit, struct jit_block *block) {
+static void jit_invalidate_block(struct jit *jit, struct jit_block *block, int reason) {
+  block->invalidate_reason = reason;
+
   jit->backend->invalidate_code(jit->backend, block->guest_addr);
 
   jit_restore_edges(jit, block);
@@ -165,7 +167,7 @@ static void jit_cache_block(struct jit *jit, struct jit_block *block) {
 }
 
 static void jit_free_block(struct jit *jit, struct jit_block *block) {
-  jit_invalidate_block(jit, block);
+  jit_invalidate_block(jit, block, JIT_REASON_UNKNOWN);
 
   rb_unlink(&jit->blocks, &block->it, &block_map_cb);
   rb_unlink(&jit->reverse_blocks, &block->rit, &reverse_block_map_cb);
@@ -224,7 +226,7 @@ void jit_invalidate_blocks(struct jit *jit) {
     struct rb_node *next = rb_next(it);
 
     struct jit_block *block = container_of(it, struct jit_block, it);
-    jit_invalidate_block(jit, block);
+    jit_invalidate_block(jit, block, JIT_REASON_UNKNOWN);
 
     it = next;
   }
@@ -289,11 +291,15 @@ void jit_compile_block(struct jit *jit, uint32_t guest_addr) {
   fastmem = 0;
 #endif
 
-  /* if the block being compiled had previously been invalidated by a fastmem
-     exception, finish removing it at this time and disable fastmem opts */
+  /* if the block had previously been invalidated, finish removing it now */
   struct jit_block *existing = jit_get_block(jit, guest_addr);
   if (existing) {
-    fastmem = existing->fastmem;
+    /* if the block was invalidated due to a fastmem exception, persist its
+       fastmem state */
+    if (existing->invalidate_reason == JIT_REASON_FASTMEM) {
+      fastmem = existing->fastmem;
+    }
+
     jit_free_block(jit, existing);
   }
 
@@ -360,12 +366,11 @@ static int jit_handle_exception(void *data, struct exception_state *ex) {
     return 0;
   }
 
-  /* invalidate the block so it's recompiled without fastmem optimizations
-     on the next access. note, the block can't be removed from the lookup
-     maps at this point because it's still executing and may raise more
-     exceptions */
+  /* disable fastmem optimizations for this block on future compiles */
   block->fastmem = 0;
-  jit_invalidate_block(jit, block);
+
+  /* invalidate the block so it's recompiled on the next access */
+  jit_invalidate_block(jit, block, JIT_REASON_FASTMEM);
 
   return 1;
 }
diff --git a/src/jit/jit.h b/src/jit/jit.h
index c6553f9d..6f4125fa 100644
--- a/src/jit/jit.h
+++ b/src/jit/jit.h
@@ -18,12 +18,17 @@ typedef uint32_t (*mem_read_cb)(void *, uint32_t, uint32_t);
 typedef void (*mem_write_cb)(void *, uint32_t, uint32_t, uint32_t);
 
 enum {
-  BRANCH_STATIC,
-  BRANCH_STATIC_TRUE,
-  BRANCH_STATIC_FALSE,
-  BRANCH_DYNAMIC,
-  BRANCH_DYNAMIC_TRUE,
-  BRANCH_DYNAMIC_FALSE,
+  JIT_BRANCH_STATIC,
+  JIT_BRANCH_STATIC_TRUE,
+  JIT_BRANCH_STATIC_FALSE,
+  JIT_BRANCH_DYNAMIC,
+  JIT_BRANCH_DYNAMIC_TRUE,
+  JIT_BRANCH_DYNAMIC_FALSE,
+};
+
+enum {
+  JIT_REASON_UNKNOWN,
+  JIT_REASON_FASTMEM,
 };
 
 struct jit_block {
@@ -31,13 +36,6 @@ struct jit_block {
   uint32_t guest_addr;
   int guest_size;
 
-  /* address of compiled block in host memory */
-  void *host_addr;
-  int host_size;
-
-  /* compile with fastmem support */
-  int fastmem;
-
   /* destination address of terminating branch */
   int branch_type;
   uint32_t branch_addr;
@@ -54,6 +52,16 @@ struct jit_block {
   /* estimated number of guest cycles to execute block */
   int num_cycles;
 
+  /* compile with fastmem support */
+  int fastmem;
+
+  /* address of compiled block in host memory */
+  void *host_addr;
+  int host_size;
+
+  /* reason the block was invalidated */
+  int invalidate_reason;
+
   /* edges to other blocks */
   struct list in_edges;
   struct list out_edges;