diff --git a/src/nodes/from_str.rs b/src/nodes/from_str.rs
index 94a4af4..ba94dfa 100644
--- a/src/nodes/from_str.rs
+++ b/src/nodes/from_str.rs
@@ -11,6 +11,8 @@ impl Node {
             "c" => Self::Number(Float::with_val(PREC, 299_792_458)),
             "A" => Self::Number(Float::with_val(PREC, 6.02214076e23)),
             "pi" => Self::Number(Float::with_val(PREC, f64::consts::PI)),
+            // Planck's constant, in J*s (joule-seconds)
+            "h" => Self::Number(Float::with_val(PREC, 6.62607015e-34)),
             _ => Self::Function(s.parse()?),
         })
     }