diff --git a/disasm/isa_parser.cc b/disasm/isa_parser.cc
index 59472a43..c18a72d8 100644
--- a/disasm/isa_parser.cc
+++ b/disasm/isa_parser.cc
@@ -1,5 +1,4 @@
 #include "isa_parser.h"
-#include "extension.h"
 
 static std::string strtolower(const char* str)
 {
@@ -292,11 +291,7 @@ isa_parser_t::isa_parser_t(const char* str, const char *priv)
       if (ext_str.size() == 1) {
         bad_isa_string(str, "single 'X' is not a proper name");
       } else if (ext_str != "xdummy") {
-         extension_t* x = find_extension(ext_str.substr(1).c_str())();
-         if (!extensions.insert(std::make_pair(x->name(), x)).second) {
-           fprintf(stderr, "extensions must have unique names (got two named \"%s\"!)\n", x->name());
-           abort();
-         }
+        extensions.insert(ext_str.substr(1));
       }
     } else {
       bad_isa_string(str, ("unsupported extension: " + ext_str).c_str());
diff --git a/riscv/isa_parser.h b/riscv/isa_parser.h
index 5b043475..335a42bf 100644
--- a/riscv/isa_parser.h
+++ b/riscv/isa_parser.h
@@ -6,9 +6,7 @@
 
 #include <bitset>
 #include <string>
-#include <unordered_map>
-
-class extension_t;
+#include <set>
 
 typedef enum {
   // 65('A') ~ 90('Z') is reserved for standard isa in misa
@@ -109,15 +107,14 @@ public:
 
   std::bitset<NUM_ISA_EXTENSIONS> get_extension_table() const { return extension_table; }
 
-  const std::unordered_map<std::string, extension_t*> &
-  get_extensions() const { return extensions; }
+  const std::set<std::string> &get_extensions() const { return extensions; }
 
 protected:
   unsigned max_xlen;
   reg_t max_isa;
   std::bitset<NUM_ISA_EXTENSIONS> extension_table;
   std::string isa_string;
-  std::unordered_map<std::string, extension_t*> extensions;
+  std::set<std::string> extensions;
 };
 
 #endif
diff --git a/riscv/processor.cc b/riscv/processor.cc
index 1d5675a5..e81375a2 100644
--- a/riscv/processor.cc
+++ b/riscv/processor.cc
@@ -61,7 +61,7 @@ processor_t::processor_t(const isa_parser_t *isa, const cfg_t *cfg,
 
   disassembler = new disassembler_t(isa);
   for (auto e : isa->get_extensions())
-    register_extension(e.second);
+    register_extension(find_extension(e.c_str())());
 
   set_pmp_granularity(1 << PMP_SHIFT);
   set_pmp_num(cfg->pmpregions);