diff --git a/src/base32.h b/src/base32.h
index a93f9180..203bb8b9 100644
--- a/src/base32.h
+++ b/src/base32.h
@@ -64,6 +64,8 @@ std::string decode(InputIterator first, InputIterator last)
       unsigned char value;
       if('A' <= ch && ch <= 'Z') {
         value = ch-'A';
+      } else if('a' <= ch && ch <= 'z') {
+        value = ch-'a';
       } else if('2' <= ch && ch <= '7') {
         value = ch-'2'+26;
       } else if(ch == '=') {
diff --git a/test/Base32Test.cc b/test/Base32Test.cc
index 03d52e8d..aca15b53 100644
--- a/test/Base32Test.cc
+++ b/test/Base32Test.cc
@@ -48,6 +48,9 @@ void Base32Test::testDecode()
   s = "GEZDGNBV";
   CPPUNIT_ASSERT_EQUAL(std::string("12345"),
                        base32::decode(s.begin(), s.end()));
+  s = "gezdgnbv";
+  CPPUNIT_ASSERT_EQUAL(std::string("12345"),
+                       base32::decode(s.begin(), s.end()));
 }
 
 } // namespace aria2