diff --git a/frontends/parsers/p4/p4parser.ypp b/frontends/parsers/p4/p4parser.ypp
index 52c6ddc8b96..7d392dde599 100644
--- a/frontends/parsers/p4/p4parser.ypp
+++ b/frontends/parsers/p4/p4parser.ypp
@@ -152,10 +152,10 @@ inline std::ostream& operator<<(std::ostream& out, const Token& t) {
 
 using namespace P4;
 
-#define YYLLOC_DEFAULT(Cur, Rhs, N)                                             \
-    ((Cur) = (N) ? YYRHSLOC(Rhs, 1) + YYRHSLOC(Rhs, N)                          \
-                 : Util::SourceInfo(driver.sources, YYRHSLOC(Rhs, 0).getEnd()))
-
+#define YYLLOC_DEFAULT(Cur, Rhs, N)                                                        \
+    ((Cur) = (N) ? YYRHSLOC(Rhs, 1) + YYRHSLOC(Rhs, N)                                     \
+        : YYRHSLOC(Rhs, 0) ?  Util::SourceInfo(driver.sources, YYRHSLOC(Rhs, 0).getEnd())  \
+                 : Util::SourceInfo(driver.sources, driver.sources->getCurrentPosition()))
 #undef yylex
 #define yylex lexer.yylex
 
diff --git a/frontends/parsers/parserDriver.cpp b/frontends/parsers/parserDriver.cpp
index 3e26d3f04b4..5a97d8508fc 100644
--- a/frontends/parsers/parserDriver.cpp
+++ b/frontends/parsers/parserDriver.cpp
@@ -69,7 +69,7 @@ struct AutoStdioInputStream {
 
 namespace P4 {
 
-AbstractParserDriver::AbstractParserDriver() : sources(new Util::InputSources) {}
+AbstractParserDriver::AbstractParserDriver() : sources(new Util::InputSources()) {}
 
 AbstractParserDriver::~AbstractParserDriver() {}
 
diff --git a/frontends/parsers/v1/v1parser.ypp b/frontends/parsers/v1/v1parser.ypp
index f640d1ffbb8..710acc15245 100644
--- a/frontends/parsers/v1/v1parser.ypp
+++ b/frontends/parsers/v1/v1parser.ypp
@@ -128,9 +128,10 @@ typedef const IR::Type ConstType;
 
 using namespace P4;
 
-#define YYLLOC_DEFAULT(Cur, Rhs, N)                                             \
-    ((Cur) = (N) ? YYRHSLOC(Rhs, 1) + YYRHSLOC(Rhs, N)                          \
-                 : Util::SourceInfo(driver.sources, YYRHSLOC(Rhs, 0).getEnd()))
+#define YYLLOC_DEFAULT(Cur, Rhs, N)                                                        \
+    ((Cur) = (N) ? YYRHSLOC(Rhs, 1) + YYRHSLOC(Rhs, N)                                     \
+        : YYRHSLOC(Rhs, 0) ?  Util::SourceInfo(driver.sources, YYRHSLOC(Rhs, 0).getEnd())  \
+                 : Util::SourceInfo(driver.sources, driver.sources->getCurrentPosition()))
 
 #undef yylex
 #define yylex lexer.yylex
diff --git a/lib/source_file.cpp b/lib/source_file.cpp
index 51cbd6a444a..e0551498c9e 100644
--- a/lib/source_file.cpp
+++ b/lib/source_file.cpp
@@ -51,12 +51,24 @@ cstring SourcePosition::toString() const {
 SourceInfo::SourceInfo(const InputSources *sources, SourcePosition start, SourcePosition end)
     : sources(sources), start(start), end(end) {
     BUG_CHECK(sources != nullptr, "Invalid InputSources in SourceInfo");
-    if (!start.isValid() || !end.isValid())
-        BUG("Invalid source position in SourceInfo %1%-%2%", start.toString(), end.toString());
+    if (!start.isValid() || !end.isValid()) {
+        BUG("Invalid source position in SourceInfo %1%-%2% for %3%", start.toString(),
+            end.toString(), sources->toDebugString());
+    }
     if (start > end)
         BUG("SourceInfo position start %1% after end %2%", start.toString(), end.toString());
 }
 
+SourceInfo::SourceInfo(const InputSources *sources, SourcePosition point)
+    : SourceInfo(sources, point, point) {}
+
+SourceInfo::SourceInfo(cstring filename, int line, int column, cstring srcBrief) {
+    this->filename = filename;
+    this->line = line;
+    this->column = column;
+    this->srcBrief = srcBrief;
+}
+
 cstring SourceInfo::toString() const {
     return absl::StrFormat("(%v)-(%v)", start.toString(), end.toString());
 }
diff --git a/lib/source_file.h b/lib/source_file.h
index f10118d3eb2..7636ffd2640 100644
--- a/lib/source_file.h
+++ b/lib/source_file.h
@@ -135,18 +135,12 @@ class SourceInfo final {
     int line = -1;
     int column = -1;
     cstring srcBrief = ""_cs;
-    SourceInfo(cstring filename, int line, int column, cstring srcBrief) {
-        this->filename = filename;
-        this->line = line;
-        this->column = column;
-        this->srcBrief = srcBrief;
-    }
+    SourceInfo(cstring filename, int line, int column, cstring srcBrief);
     /// Creates an "invalid" SourceInfo
     SourceInfo() = default;
 
     /// Creates a SourceInfo for a 'point' in the source, or invalid
-    SourceInfo(const InputSources *sources, SourcePosition point)
-        : sources(sources), start(point), end(point) {}
+    SourceInfo(const InputSources *sources, SourcePosition point);
 
     SourceInfo(const InputSources *sources, SourcePosition start, SourcePosition end);
 
diff --git a/tools/ir-generator/ir-generator.ypp b/tools/ir-generator/ir-generator.ypp
index 3dd060bccbc..3e59052f1ec 100644
--- a/tools/ir-generator/ir-generator.ypp
+++ b/tools/ir-generator/ir-generator.ypp
@@ -39,9 +39,10 @@ limitations under the License.
 namespace P4 {
 
 #define YYLTYPE Util::SourceInfo
-#define YYLLOC_DEFAULT(Cur, Rhs, N)                                     \
-    ((Cur) = (N) ? YYRHSLOC(Rhs, 1) + YYRHSLOC(Rhs, N)                  \
-                 : Util::SourceInfo(sources, YYRHSLOC(Rhs, 0).getEnd()))
+#define YYLLOC_DEFAULT(Cur, Rhs, N)                                                     \
+    ((Cur) = (N) ? YYRHSLOC(Rhs, 1) + YYRHSLOC(Rhs, N)                                  \
+        : yylloc ? yyloc                                                                \
+                 : Util::SourceInfo(sources, sources->getCurrentPosition()))
 
 template<typename... Args>
 void yyerror(const char *fmt, Args&&... args);