diff --git a/scikits/image/graph/_mcp.pyx b/scikits/image/graph/_mcp.pyx
index c1a6429e..47c704fc 100644
--- a/scikits/image/graph/_mcp.pyx
+++ b/scikits/image/graph/_mcp.pyx
@@ -476,19 +476,26 @@ cdef class MCP:
                 # ignore this point
                 if flat_cumulative_costs[new_index] != inf:
                     continue
-
+                # If the cost at this point is negative or infinite, ignore it
+                new_cost = flat_costs[new_index]
+                if new_cost < 0 or new_cost == inf:
+                    continue
+                
                 # Now we ask the heap to append or update the cost to
                 # this new point, but only if that point isn't already
                 # in the heap, or it is but the new cost is lower.
                 travel_cost = self._travel_cost(flat_costs[index],
-                                                flat_costs[new_index],
+                                                new_cost,
                                                 offset_lengths[i])
-                costs_heap.push_if_lower_fast(cost + travel_cost, new_index)
-                # If we did perform an append or update, we should
-                # record the offset from the predecessor to this new
-                # point
-                if costs_heap._pushed:
-                    traceback_offsets[new_index] = i
+                # don't push infs into the heap though!
+                new_cost = cost + travel_cost
+                if new_cost != inf:
+                    costs_heap.push_if_lower_fast(new_cost, new_index)
+                    # If we did perform an append or update, we should
+                    # record the offset from the predecessor to this new
+                    # point
+                    if costs_heap._pushed:
+                        traceback_offsets[new_index] = i
 
         # Un-flatten the costs and traceback arrays for human consumption.
         cumulative_costs = flat_cumulative_costs.reshape(self.costs_shape,
diff --git a/scikits/image/graph/heap.pxd b/scikits/image/graph/heap.pxd
index b86a0027..5f3b17ee 100644
--- a/scikits/image/graph/heap.pxd
+++ b/scikits/image/graph/heap.pxd
@@ -22,7 +22,7 @@ cdef class BinaryHeap:
     cdef void _remove(self, int i)
     
     cdef int push_fast(self, double value, int reference)
-    cdef float pop_fast(self)
+    cdef VALUE_T pop_fast(self)
 
 cdef class FastUpdateBinaryHeap(BinaryHeap):
     cdef readonly int max_reference
@@ -30,6 +30,6 @@ cdef class FastUpdateBinaryHeap(BinaryHeap):
     cdef int _invalid_ref
     cdef int _pushed
     
-    cdef float value_of_fast(self, int reference)
+    cdef VALUE_T value_of_fast(self, int reference)
     cdef int push_if_lower_fast(self, double value, int reference)
     
\ No newline at end of file
diff --git a/scikits/image/graph/heap.pyx b/scikits/image/graph/heap.pyx
index 2345f2f9..59822a26 100644
--- a/scikits/image/graph/heap.pyx
+++ b/scikits/image/graph/heap.pyx
@@ -339,7 +339,7 @@ cdef class BinaryHeap:
         return count
 
 
-    cdef float pop_fast(self):
+    cdef VALUE_T pop_fast(self):
         """The c-method for fast popping.
 
         Returns the minimum value. The reference is put in self._popped_ref"""
@@ -366,7 +366,7 @@ cdef class BinaryHeap:
 
         # get values
         cdef int ir = i - ((1 << levels) - 1) #(2**self.levels-1) # LevelStart
-        cdef float value =  values[i]
+        cdef VALUE_T value =  values[i]
         self._popped_ref = self._references[ir]
 
         # remove it
@@ -645,7 +645,7 @@ cdef class FastUpdateBinaryHeap(BinaryHeap):
         return ir
 
 
-    cdef float value_of_fast(self, int reference):
+    cdef VALUE_T value_of_fast(self, int reference):
         """Return the value corresponding to the given reference. If inf
         is returned, the reference may be invalid: check the _invaild_ref
         field in this case."""