diff --git a/src/interactive.c b/src/interactive.c
index 86e1f86..5f1f8f7 100644
--- a/src/interactive.c
+++ b/src/interactive.c
@@ -78,10 +78,12 @@ libab_result register_functions(libab* ab) {
     libab_ref trig_type;
     libab_ref atan2_type;
     libab_ref difficult_type;
+    libab_ref print_num_type;
 
     result = libab_create_type(ab, &trig_type, "(num)->num");
     TRY(libab_create_type(ab, &atan2_type, "(num, num)->num"));
     TRY(libab_create_type(ab, &difficult_type, "((num)->num)->num"));
+    TRY(libab_create_type(ab, &print_num_type, "(num)->unit"));
 
     TRY(libab_register_function(ab, "atan", &trig_type, function_atan));
     TRY(libab_register_function(ab, "atan2", &atan2_type, function_atan2));
@@ -89,7 +91,7 @@ libab_result register_functions(libab* ab) {
     TRY(libab_register_function(ab, "minus", &atan2_type, function_minus));
     TRY(libab_register_function(ab, "times", &atan2_type, function_times));
     TRY(libab_register_function(ab, "divide", &atan2_type, function_divide));
-    TRY(libab_register_function(ab, "print", &trig_type, function_print_num));
+    TRY(libab_register_function(ab, "print", &print_num_type, function_print_num));
     TRY(libab_register_operator_infix(ab, "+", 0, -1, "plus"));
     TRY(libab_register_operator_infix(ab, "-", 0, -1, "minus"));
     TRY(libab_register_operator_infix(ab, "*", 1, -1, "times"));
@@ -98,6 +100,7 @@ libab_result register_functions(libab* ab) {
     libab_ref_free(&trig_type);
     libab_ref_free(&atan2_type);
     libab_ref_free(&difficult_type);
+    libab_ref_free(&print_num_type);
 
     return result;
 }