diff --git a/include/mruby/variable.h b/include/mruby/variable.h
index 0a7b7b42e..2af62f048 100644
--- a/include/mruby/variable.h
+++ b/include/mruby/variable.h
@@ -7,6 +7,12 @@
 #ifndef MRUBY_VARIABLE_H
 #define MRUBY_VARIABLE_H
 
+#if defined(__GNUC__) || defined(__clang__)
+#define MRB_MEM_PREFETCH(addr) __builtin_prefetch(addr, 0, 1)
+#else
+#define MRB_MEM_PREFETCH(addr)
+#endif
+
 #include "common.h"
 
 /**
diff --git a/src/class.c b/src/class.c
index c2bffeaf9..a23b87447 100644
--- a/src/class.c
+++ b/src/class.c
@@ -105,6 +105,8 @@ bsearch_idx(mrb_sym *keys, int size, mrb_sym target)
   /* While more than one element remains, halve the range each iteration */
   while (n > 1) {
     int half = n >> 1;
+    MRB_MEM_PREFETCH(p + (half >> 1));
+    MRB_MEM_PREFETCH(p + half + (half >> 1));
     mrb_sym mid_sym = MT_KEY_SYM(p[half]);
     /*
      * Update pointer p without a branch:
diff --git a/src/variable.c b/src/variable.c
index 4f4d9e123..75f5254b3 100644
--- a/src/variable.c
+++ b/src/variable.c
@@ -78,6 +78,8 @@ bsearch_idx(mrb_sym *keys, int size, mrb_sym target) {
   /* While more than one element remains, halve the range each iteration */
   while (n > 1) {
     int half = n >> 1;
+    MRB_MEM_PREFETCH(p + (half >> 1));
+    MRB_MEM_PREFETCH(p + half + (half >> 1));
     mrb_sym mid_sym = p[half];
     /*
      * Update pointer p without a branch: