diff --git a/src/nodes/from_str.rs b/src/nodes/from_str.rs
index 4608e48..c606454 100644
--- a/src/nodes/from_str.rs
+++ b/src/nodes/from_str.rs
@@ -6,8 +6,8 @@ use crate::nodes::{Node, Nodes, PREC};
 
 #[derive(Clone, Debug, thiserror::Error)]
 pub enum Error {
-    #[error("invalid function: {0}")]
-    InvalidFunction(String),
+    #[error("unrecognized function/constant: {0}")]
+    UnrecognizedName(String),
     #[error("invalid operator: {0}")]
     InvalidOperator(char),
     #[error("failed to parse number '{0}': {1}")]
@@ -66,7 +66,9 @@ impl FromStr for Nodes {
                 ParsingState::ReadingFunctionName(start_index) => {
                     if !c.is_alphabetic() {
                         nodes.push(Node::from_name(&filtered_string[start_index..i]).map_err(
-                            |()| Error::InvalidFunction(filtered_string[start_index..i].to_owned()),
+                            |()| {
+                                Error::UnrecognizedName(filtered_string[start_index..i].to_owned())
+                            },
                         )?);
 
                         state = ParsingState::Start;
@@ -117,7 +119,7 @@ impl FromStr for Nodes {
             ParsingState::ReadingFunctionName(start_index) => {
                 nodes.push(
                     Node::from_name(&filtered_string[start_index..i]).map_err(|()| {
-                        Error::InvalidFunction(filtered_string[start_index..i].to_owned())
+                        Error::UnrecognizedName(filtered_string[start_index..i].to_owned())
                     })?,
                 );
             }