diff --git a/src/libexpr/nix_api_expr.h b/src/libexpr/nix_api_expr.h
index 90aec8d18..f99fee1b1 100644
--- a/src/libexpr/nix_api_expr.h
+++ b/src/libexpr/nix_api_expr.h
@@ -41,7 +41,7 @@ typedef void Value; // nix::Value
  */
 typedef struct GCRef GCRef; // void*
 
-// Function propotypes
+// Function prototypes
 /**
  * @brief Initializes the Nix expression evaluator.
  *
@@ -76,7 +76,8 @@ Expr *nix_parse_expr_from_string(nix_c_context *context, State *state,
  * @param[out] context Optional, stores error information
  * @param[in] state The state of the evaluation.
  * @param[in] expr The Nix expression to evaluate.
- * @param[in] value The result of the evaluation.
+ * @param[out] value The result of the evaluation. You should allocate this
+ * yourself.
  * @return NIX_OK if the evaluation was successful, an error code otherwise.
  */
 nix_err nix_expr_eval(nix_c_context *context, State *state, Expr *expr,
diff --git a/src/libstore/nix_api_store.h b/src/libstore/nix_api_store.h
index 1ab7a4eb7..ba7b9ec5e 100644
--- a/src/libstore/nix_api_store.h
+++ b/src/libstore/nix_api_store.h
@@ -1,7 +1,7 @@
 #ifndef NIX_API_STORE_H
 #define NIX_API_STORE_H
 /** @file
- * @brief Main entry for the libexpr C bindings
+ * @brief Main entry for the libstore C bindings
  */
 
 #include "nix_api_util.h"