diff --git a/requirements_dev.txt b/requirements_dev.txt
index 35552e9..a674153 100644
--- a/requirements_dev.txt
+++ b/requirements_dev.txt
@@ -3,4 +3,4 @@ cython
 sphinx
 # virtualenv < 14 is required to keep the Python 3.2 builds running
 virtualenv<14
-tox==2.1.1
+tox<3
diff --git a/src/fuzzysearch/memmem.c b/src/fuzzysearch/memmem.c
index 16a36f0..336674f 100644
--- a/src/fuzzysearch/memmem.c
+++ b/src/fuzzysearch/memmem.c
@@ -89,7 +89,7 @@ char *simple_memmem(const char *haystack, size_t haystacklen,
     return NULL;
 }
 
-void *simple_memmem_with_needle_sum(const char *haystack, size_t haystacklen,
+char *simple_memmem_with_needle_sum(const char *haystack, size_t haystacklen,
                                     const char *needle, size_t needlelen,
                                     int needle_sum)
 {
diff --git a/tox.ini b/tox.ini
index a5fc366..9c5f135 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,16 +19,16 @@ deps =
     py{27,33,34,35,36}: biopython
 whitelist_externals =
     mv
-    cat
-    find
+;    cat
+;    find
 commands =
     ; Notes:
     ; * run tests both with and without the C extensions (including Cython)
     ; * if running with coverage, merge the coverage run results from both runs
     ; * for Python 2.6 use the unit2 script since -m unittest2 doesn't work
     ;     (but when running with coverage, coverage run -m unittest2 works)
-    find {envlogdir} -type f -name '*.log' -printf "\n%p\n" -exec cat \{\} \;
-    echo "++++++++++++++++++++++++++++++++++++++"
+;    find {envlogdir} -type f -name '*.log' -printf "\n%p\n" -exec cat \{\} \;
+;    echo "++++++++++++++++++++++++++++++++++++++"
     py26-without_coverage: {envbindir}/unit2 discover tests -t {toxinidir}
     py26-with_coverage: {envbindir}/coverage run --source=fuzzysearch -m unittest2 discover tests
     py{27,32,33,34,35,36}-without_coverage: {envpython} -m unittest discover tests