diff --git a/configure.ac b/configure.ac
index 7a83d8f35..7a1c283a2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -126,6 +126,10 @@ NEED_PROG(perl, perl)
 NEED_PROG(tar, tar)
 AC_PATH_PROG(dot, dot)
 
+AC_PATH_PROG(openssl_prog, openssl, openssl) # if not found, call openssl in $PATH
+AC_SUBST(openssl_prog)
+AC_DEFINE_UNQUOTED(OPENSSL_PATH, ["$openssl_prog"], [Path of the OpenSSL binary])
+
 # Test that Perl has the open/fork feature (Perl 5.8.0 and beyond).
 AC_MSG_CHECKING([whether Perl is recent enough])
 if ! $perl -e 'open(FOO, "-|", "true"); while (<FOO>) { print; }; close FOO or die;'; then
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index edbe567f4..0bf246f1e 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -776,7 +776,7 @@ void LocalStore::exportPath(const Path & path, bool sign,
         args.push_back(secretKey);
         args.push_back("-in");
         args.push_back(hashFile);
-        string signature = runProgram("openssl", true, args);
+        string signature = runProgram(OPENSSL_PATH, true, args);
 
         writeString(signature, hashAndWriteSink);
         
@@ -852,7 +852,7 @@ Path LocalStore::importPath(bool requireSignature, Source & source)
             args.push_back("-pubin");
             args.push_back("-in");
             args.push_back(sigFile);
-            string hash2 = runProgram("openssl", true, args);
+            string hash2 = runProgram(OPENSSL_PATH, true, args);
 
             /* Note: runProgram() throws an exception if the signature
                is invalid. */