diff --git a/patcherex/cfg_utils.py b/patcherex/cfg_utils.py
index 9d265bd..e04a3be 100644
--- a/patcherex/cfg_utils.py
+++ b/patcherex/cfg_utils.py
@@ -80,7 +80,7 @@ def check_first_instruction(instr):
         return None
 
     try:
-        succ = ff.startpoint.successors()
+        outedges = ff.transition_graph.out_edges(ff.startpoint, data=True)
     except networkx.NetworkXError:
         return None
     ends = ff.endpoints
@@ -90,19 +90,21 @@ def check_first_instruction(instr):
         return None
 
     if syscall_number == 1:
-        if len(succ) == 1:
-            bb1 = succ[0]
-            if hasattr(bb1,"is_syscall") and bb1.is_syscall:
+        if len(outedges) == 1:
+            edge_data = list(outedges)[0][-1]
+            if edge_data.get("type") == "syscall":
                 return syscall_number
         return None
     else:
         if not is_sane_function(ff):
             return None
-        if len(succ) == 2:
-            bb1,bb2 = succ
-            if hasattr(bb1,"is_syscall") and bb1.is_syscall:
+        if len(outedges) == 2:
+            outedges = list(outedges)
+            _, bb1, data1 = outedges[0]
+            _, bb2, data2 = outedges[1]
+            if data1.get("type") == "syscall":
                 ebb = bb2
-            elif hasattr(bb2,"is_syscall") and bb2.is_syscall:
+            elif data2.get("type") == "syscall":
                 ebb = bb1
             else:
                 ebb= None
diff --git a/tests/test_cfg.py b/tests/test_cfg.py
index 8af86d0..fb1806b 100755
--- a/tests/test_cfg.py
+++ b/tests/test_cfg.py
@@ -261,7 +261,7 @@ def test_detect_syscall_wrapper():
     syscall_wrappers = set([(ff.addr,cfg_utils.detect_syscall_wrapper(backend,ff)) \
             for ff in cfg.functions.values() if cfg_utils.detect_syscall_wrapper(backend,ff)!=None])
     print("syscall wrappers in CROMU_00071:")
-    print(map(lambda x:(hex(x[0]),x[1]),syscall_wrappers))
+    print(list(map(lambda x:(hex(x[0]),x[1]),syscall_wrappers)))
     assert syscall_wrappers == legitimate_syscall_wrappers
 
     filepath = os.path.join(bin_location, "CROMU_00070")
@@ -280,7 +280,7 @@ def test_detect_syscall_wrapper():
     syscall_wrappers = set([(ff.addr,cfg_utils.detect_syscall_wrapper(backend,ff)) \
             for ff in cfg.functions.values() if cfg_utils.detect_syscall_wrapper(backend,ff)!=None])
     print("syscall wrappers in CROMU_00070:")
-    print(map(lambda x:(hex(x[0]),x[1]),syscall_wrappers))
+    print(list(map(lambda x:(hex(x[0]),x[1]),syscall_wrappers)))
     assert syscall_wrappers == legitimate_syscall_wrappers