diff --git a/ffi/src/helpers.rs b/ffi/src/helpers.rs
index 08f5759..18545d9 100644
--- a/ffi/src/helpers.rs
+++ b/ffi/src/helpers.rs
@@ -23,6 +23,7 @@ pub fn handle_error(err: Error) -> c_int {
 fn map_error(err: &Error) -> c_int {
     match err {
         Error::ParsingIncomplete => LCI_ERROR_PARSING_ERROR,
+        Error::UnconsumedInput(_) => LCI_ERROR_PARSING_ERROR,
         Error::GenericParsingError(_, _) => LCI_ERROR_PARSING_ERROR,
         Error::CustomParsingError(_, _) => LCI_ERROR_PARSING_ERROR,
         Error::PeParsingError(_, _) => LCI_ERROR_PE_PARSING_ERROR,
diff --git a/src/error.rs b/src/error.rs
index 2c78463..f68eb8d 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -10,6 +10,8 @@ use regex;
 #[derive(Debug)]
 pub enum Error {
     ParsingIncomplete,
+    // The string is the input that was not parsed.
+    UnconsumedInput(String),
     /// The first string is the expression parsed, the second is a tag describing the parser that failed.
     GenericParsingError(String, String),
     /// The string is the expression parsed.
@@ -41,6 +43,11 @@ impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
             Error::ParsingIncomplete => write!(f, "More input was expected by the parser"),
+            Error::UnconsumedInput(i) => write!(
+                f,
+                "The parser did not consume the following input: \"{}\"",
+                i
+            ),
             Error::GenericParsingError(i, e) => write!(
                 f,
                 "An error was encountered in the parser \"{}\" while parsing the expression \"{}\"",
diff --git a/src/lib.rs b/src/lib.rs
index ae79d4f..5a9ca41 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -161,8 +161,14 @@ impl str::FromStr for Expression {
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         parse_expression(nom::types::CompleteStr(s))
-            .map(|(_, expression)| expression)
             .map_err(Error::from)
+            .and_then(|(remaining_input, expression)| {
+                if remaining_input.is_empty() {
+                    Ok(expression)
+                } else {
+                    Err(Error::UnconsumedInput(remaining_input.to_string()))
+                }
+            })
     }
 }
 
@@ -502,6 +508,16 @@ mod tests {
         }
     }
 
+    #[test]
+    fn expression_parse_should_error_if_it_does_not_consume_the_whole_input() {
+        let error = Expression::from_str("file(\"Cargo.toml\") foobar").unwrap_err();
+
+        assert_eq!(
+            "The parser did not consume the following input: \" foobar\"",
+            error.to_string()
+        );
+    }
+
     #[test]
     fn compound_condition_parse_should_handle_a_single_condition() {
         let result = CompoundCondition::parse("file(\"Cargo.toml\")".into())