diff --git a/src/coordinax/_src/vectors/checks.py b/src/coordinax/_src/vectors/checks.py
index 14d9ae69..7b6fa3d7 100644
--- a/src/coordinax/_src/vectors/checks.py
+++ b/src/coordinax/_src/vectors/checks.py
@@ -101,7 +101,7 @@ def check_non_negative(x: AbstractQuantity, /, name: str = "") -> AbstractQuanti
 
     """
     name = f" {name}" if name else name
-    return eqx.error_if(x, xp.any(x < 0), "The input{name} must be non-negative.")
+    return eqx.error_if(x, xp.any(x < 0), f"The input{name} must be non-negative.")
 
 
 def check_non_negative_non_zero(
@@ -132,7 +132,7 @@ def check_non_negative_non_zero(
     """
     name = f" {name}" if name else name
     return eqx.error_if(
-        x, xp.any(x <= 0), "The input{name} must be non-negative and non-zero."
+        x, xp.any(x <= 0), f"The input{name} must be non-negative and non-zero."
     )