diff --git a/src/FEQParse.F90 b/src/FEQParse.F90
index 1674796..886e85d 100644
--- a/src/FEQParse.F90
+++ b/src/FEQParse.F90
@@ -572,11 +572,9 @@ function Evaluate_sfp64(parser,x) result(f)
       case(Monadic_Token)
 
         if(trim(t%tokenString) == '-') then
-
           call stack%Pop(a)
           a = -a
           call stack%Push(a)
-
         endif
 
       case default
@@ -1670,21 +1668,33 @@ integer function Priority(parser,toke)
 
       Priority = 5
 
-    elseif(toke%tokenString(1:1) == '^') then
+    elseif(toke%tokenType == Operator_Token) then
+
+      if(toke%tokenString(1:1) == '^') then
 
-      Priority = 4
+        Priority = 4
 
-    elseif(toke%tokenString(1:1) == '/') then
+      elseif(toke%tokenString(1:1) == '/') then
 
-      Priority = 3
+        Priority = 3
 
-    elseif(toke%tokenString(1:1) == '*') then
+      elseif(toke%tokenString(1:1) == '*') then
 
-      Priority = 2
+        Priority = 2
 
-    elseif(toke%tokenString(1:1) == '+' .or. toke%tokenString(1:1) == '-') then
+      elseif(toke%tokenString(1:1) == '+' .or. toke%tokenString(1:1) == '-') then
+
+        Priority = 1
+
+      else
 
-      Priority = 1
+        Priority = 0
+
+      endif
+
+    elseif(toke%tokenType == Monadic_Token) then
+
+      Priority = 5
 
     else
 
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 53ccb26..4be87dd 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -189,5 +189,6 @@ add_fortran_tests (
     "tan_sfp64.f90"
     "print_tokens.f90"
     "custom_r1fp64.f90"
-    "parsing_difficult_r1fp64.f90")
+    "parsing_difficult_r1fp64.f90"
+    "parsing_vanderpol_sfp64.f90")
     
\ No newline at end of file
diff --git a/test/parsing_vanderpol_sfp64.f90 b/test/parsing_vanderpol_sfp64.f90
new file mode 100644
index 0000000..a8b0843
--- /dev/null
+++ b/test/parsing_vanderpol_sfp64.f90
@@ -0,0 +1,51 @@
+program test
+
+  implicit none
+  integer :: exit_code
+
+  exit_code = vanderpol_sfp64()
+  stop exit_code
+
+contains
+
+  integer function vanderpol_sfp64() result(r)
+    use FEQParse
+    use iso_fortran_env
+    implicit none
+    integer,parameter :: N = 10
+    type(EquationParser) :: f
+    character(len=128) :: fun_buf
+    real(real64) :: t,x,y,u,v
+    real(real64) :: feval
+    real(real64) :: fexact
+
+    fun_buf = '-8.53*(1-x*x)*v-y'
+    f = equationparser('f = '//fun_buf,['t','x','y','u','v'])
+
+    print*,"--------- Infix -------------------"
+    call f%Print_InFixTokens()
+    print*,"-----------------------------------"
+    print*,"--------- Postfix -------------------"
+    call f%Print_PostFixTokens()
+    print*,"-----------------------------------"
+
+    t = 0.0_real64
+    x = 1.0_real64
+    y = 3.0_real64
+    u = 12.0_real64
+    v = 0.0_real64
+
+    feval = f%evaluate([t,x,y,u,v])
+
+    fexact = -8.53_real64*(1.0_real64-x*x)*v-y
+
+    if((abs(feval-fexact)) <= epsilon(1.0_real64)) then
+      r = 0
+      print*,feval,fexact
+    else
+      r = 1
+      print*,feval,fexact
+    endif
+
+  endfunction vanderpol_sfp64
+endprogram test