diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 4a1b346ef..3917fffc3 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -203,8 +203,6 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
 
     std::ostringstream oss;
 
-    auto noSource = ANSI_ITALIC " (source not available)" ANSI_NORMAL "\n";
-
     /*
      * Traces
      * ------
@@ -320,7 +318,7 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
 
             oss << "\n" << "… " << trace.hint.str() << "\n";
 
-            if (trace.pos) {
+            if (trace.pos && *trace.pos) {
                 count++;
 
                 oss << "\n" << ellipsisIndent << ANSI_BLUE << "at " ANSI_WARNING << *trace.pos << ANSI_NORMAL << ":";
@@ -329,8 +327,7 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
                     oss << "\n";
                     printCodeLines(oss, "", *trace.pos, *loc);
                     oss << "\n";
-                } else
-                    oss << noSource;
+                }
             }
         }
         oss << "\n" << prefix;
@@ -338,15 +335,14 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
 
     oss << einfo.msg << "\n";
 
-    if (einfo.errPos) {
+    if (einfo.errPos && *einfo.errPos) {
         oss << "\n" << ANSI_BLUE << "at " ANSI_WARNING << *einfo.errPos << ANSI_NORMAL << ":";
 
         if (auto loc = einfo.errPos->getCodeLines()) {
             oss << "\n";
             printCodeLines(oss, "", *einfo.errPos, *loc);
             oss << "\n";
-        } else
-            oss << noSource;
+        }
     }
 
     auto suggestions = einfo.suggestions.trim();
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index be5c5e252..c04dcbd77 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -70,6 +70,13 @@ struct AbstractPos
     uint32_t line = 0;
     uint32_t column = 0;
 
+    /**
+     * An AbstractPos may be a "null object", representing an unknown position.
+     *
+     * Return true if this position is known.
+     */
+    inline operator bool() const { return line != 0; };
+
     /**
      * Return the contents of the source file.
      */
diff --git a/tests/lang/eval-fail-fromTOML-timestamps.err.exp b/tests/lang/eval-fail-fromTOML-timestamps.err.exp
index f6bd19f5a..5b60d253d 100644
--- a/tests/lang/eval-fail-fromTOML-timestamps.err.exp
+++ b/tests/lang/eval-fail-fromTOML-timestamps.err.exp
@@ -8,5 +8,3 @@ error:
             2|   key = "value"
 
        error: while parsing a TOML string: Dates and times are not supported
-
-       at «none»:0: (source not available)
diff --git a/tests/lang/eval-fail-hashfile-missing.err.exp b/tests/lang/eval-fail-hashfile-missing.err.exp
index 8e77dec1e..6d38608c0 100644
--- a/tests/lang/eval-fail-hashfile-missing.err.exp
+++ b/tests/lang/eval-fail-hashfile-missing.err.exp
@@ -10,10 +10,6 @@ error:
 
        … while evaluating the first argument passed to builtins.toString
 
-         at «none»:0: (source not available)
-
        … while calling the 'hashFile' builtin
 
-         at «none»:0: (source not available)
-
        error: opening file '/pwd/lang/this-file-is-definitely-not-there-7392097': No such file or directory
diff --git a/tests/lang/eval-fail-set-override.err.exp b/tests/lang/eval-fail-set-override.err.exp
index beb29d678..71481683d 100644
--- a/tests/lang/eval-fail-set-override.err.exp
+++ b/tests/lang/eval-fail-set-override.err.exp
@@ -1,6 +1,4 @@
 error:
        … while evaluating the `__overrides` attribute
 
-         at «none»:0: (source not available)
-
        error: value is an integer while a set was expected
diff --git a/tests/lang/eval-fail-substring.err.exp b/tests/lang/eval-fail-substring.err.exp
index dc26a00bd..5c58be29a 100644
--- a/tests/lang/eval-fail-substring.err.exp
+++ b/tests/lang/eval-fail-substring.err.exp
@@ -8,5 +8,3 @@ error:
             2|
 
        error: negative start position in 'substring'
-
-       at «none»:0: (source not available)
diff --git a/tests/lang/eval-fail-to-path.err.exp b/tests/lang/eval-fail-to-path.err.exp
index 43ed2bdfc..4ffa2cf6d 100644
--- a/tests/lang/eval-fail-to-path.err.exp
+++ b/tests/lang/eval-fail-to-path.err.exp
@@ -9,6 +9,4 @@ error:
 
        … while evaluating the first argument passed to builtins.toPath
 
-         at «none»:0: (source not available)
-
        error: string 'foo/bar' doesn't represent an absolute path