diff --git a/pyedflib/_extensions/_pyedflib.pyx b/pyedflib/_extensions/_pyedflib.pyx
index edbac53..d3b9625 100644
--- a/pyedflib/_extensions/_pyedflib.pyx
+++ b/pyedflib/_extensions/_pyedflib.pyx
@@ -277,7 +277,7 @@ cdef class CyEdfReader:
     property gender:
         def __get__(self):
             warnings.warn("Variable 'gender' is deprecated, use 'sex' instead.", DeprecationWarning, stacklevel=2)
-            return self.hdr.gender
+            return self.hdr.sex
 
     property birthdate:
         def __get__(self):
@@ -598,11 +598,11 @@ def rewind(handle, edfsignal):
 def set_sex(handle, sex):
     """int edf_set_sex(int handle, int sex)"""
     if sex is None: return 0 #don't set sex at all to prevent default 'F'
-    return c_edf.edf_set_gender(handle, sex)
+    return c_edf.edf_set_sex(handle, sex)
 
 def set_gender(handle, gender):
     warnings.warn("Function 'set_gender' is deprecated, use 'set_sex' instead.", DeprecationWarning, stacklevel=2)
-    return set_sex(handle, gender)
+    return c_edf.edf_set_sex(handle, gender)
 
 def set_physical_dimension(handle, edfsignal, phys_dim):
     """int edf_set_physical_dimension(int handle, int edfsignal, const char *phys_dim)"""
diff --git a/pyedflib/_extensions/c_edf.pxd b/pyedflib/_extensions/c_edf.pxd
index 10de6c0..ba767e8 100644
--- a/pyedflib/_extensions/c_edf.pxd
+++ b/pyedflib/_extensions/c_edf.pxd
@@ -57,7 +57,7 @@ cdef extern from "c/edflib.h":
         char * patient
         char * recording
         char * patientcode
-        char * gender
+        char * sex
         char * birthdate
         char * patient_name
         char * patient_additional
@@ -81,7 +81,7 @@ cdef extern from "c/edflib.h":
     int edf_blockwrite_digital_samples(int, int *)
     long long int edftell(int, int)
     void edfrewind(int, int)
-    int edf_set_gender(int, int)
+    int edf_set_sex(int, int)
     int edf_set_physical_dimension(int, int, char *)
     int edf_set_transducer(int, int, char *)
     int edf_set_prefilter(int, int, char *)