diff --git a/praxes/io/spec/proxies.pyx b/praxes/io/spec/proxies.pyx
index e3ce300..c42f292 100644
--- a/praxes/io/spec/proxies.pyx
+++ b/praxes/io/spec/proxies.pyx
@@ -116,7 +116,7 @@ cdef class DataProxy:
             j = 0
             val_n = 0
             for c in cstring:
-                if isdigit(c) or c in (b'-', b'.', b'e', b'E'):
+                if isdigit(c) or c in (b'-', b'+', b'.', b'e', b'E'):
                     val[j] = c
                     j += 1
                 elif j: