diff --git a/src/algorithm.F90 b/src/algorithm.F90
index 101b11b9a..1687f1365 100644
--- a/src/algorithm.F90
+++ b/src/algorithm.F90
@@ -261,7 +261,11 @@ contains
     integer,         intent(in) :: val
     integer                     :: index
 
-    index = find_int(vec % data(1:vec % size()), val)
+    if (vec % size() > 0) then
+      index = find_int(vec % data(1:vec % size()), val)
+    else
+      index = -1
+    end if
   end function find_vector_int
 
   pure function find_vector_real(vec, val) result(index)
@@ -269,7 +273,11 @@ contains
     real(8),          intent(in) :: val
     integer                      :: index
 
-    index = find_real(vec % data(1:vec % size()), val)
+    if (vec % size() > 0) then
+      index = find_real(vec % data(1:vec % size()), val)
+    else
+      index = -1
+    end if
   end function find_vector_real
 
 end module algorithm