diff --git a/mex/sources/build_matlab.m b/mex/sources/build_matlab.m
index 71ed466a2..71fc39495 100644
--- a/mex/sources/build_matlab.m
+++ b/mex/sources/build_matlab.m
@@ -72,7 +72,7 @@ end
 
 if matlab_ver_less_than('7.5')
     OUTPUT_DIR = '../2007a';
-elseif matlab_ver_less_than('7.8') || ~regexp(computer, '.*64')
+elseif matlab_ver_less_than('7.8') || isempty(regexp(computer, '.*64','ONCE'))
     OUTPUT_DIR = '../2007b';
 else
     OUTPUT_DIR = '../2009a-64bit';
diff --git a/mex/sources/build_matlab_multithread.m b/mex/sources/build_matlab_multithread.m
index dd2c823f8..95d1555bf 100644
--- a/mex/sources/build_matlab_multithread.m
+++ b/mex/sources/build_matlab_multithread.m
@@ -72,7 +72,7 @@ end
 
 if matlab_ver_less_than('7.5')
     OUTPUT_DIR = '../2007a';
-elseif matlab_ver_less_than('7.8') || ~regexp(computer, '.*64')
+elseif matlab_ver_less_than('7.8') || isempty(regexp(computer, '.*64','ONCE'))
     OUTPUT_DIR = '../2007b';
 else
     OUTPUT_DIR = '../2009a-64bit';