diff --git a/src/string.cpp b/src/string.cpp
index 59785cfe90..191d9924ad 100644
--- a/src/string.cpp
+++ b/src/string.cpp
@@ -368,6 +368,20 @@ bool StrEqualsIgnoreCase(const std::string_view str1, const std::string_view str
 	return StrCompareIgnoreCase(str1, str2) == 0;
 }
 
+/**
+ * Checks if a string is contained in another string, while ignoring the case of the characters.
+ *
+ * @param str The string to search in.
+ * @param value The string to search for.
+ * @return True if a match was found.
+ */
+bool StrContainsIgnoreCase(const std::string_view str, const std::string_view value)
+{
+	CaseInsensitiveStringView ci_str{ str.data(), str.size() };
+	CaseInsensitiveStringView ci_value{ value.data(), value.size() };
+	return ci_str.find(ci_value) != ci_str.npos;
+}
+
 /**
  * Get the length of an UTF-8 encoded string in number of characters
  * and thus not the number of bytes that the encoded string contains.
diff --git a/src/string_func.h b/src/string_func.h
index 25cc86489e..68fd80b45f 100644
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -36,6 +36,7 @@ std::string_view StrTrimView(std::string_view str);
 
 [[nodiscard]] int StrCompareIgnoreCase(const std::string_view str1, const std::string_view str2);
 [[nodiscard]] bool StrEqualsIgnoreCase(const std::string_view str1, const std::string_view str2);
+[[nodiscard]] bool StrContainsIgnoreCase(const std::string_view str, const std::string_view value);
 [[nodiscard]] int StrNaturalCompare(std::string_view s1, std::string_view s2, bool ignore_garbage_at_front = false);
 [[nodiscard]] bool StrNaturalContains(const std::string_view str, const std::string_view value);
 [[nodiscard]] bool StrNaturalContainsIgnoreCase(const std::string_view str, const std::string_view value);
diff --git a/src/stringfilter.cpp b/src/stringfilter.cpp
index 539a95fca4..3a3221509b 100644
--- a/src/stringfilter.cpp
+++ b/src/stringfilter.cpp
@@ -102,10 +102,8 @@ void StringFilter::ResetState()
  *
  * @param str Another line from the item.
  */
-void StringFilter::AddLine(const char *str)
+void StringFilter::AddLine(std::string_view str)
 {
-	if (str == nullptr) return;
-
 	bool match_case = this->case_sensitive != nullptr && *this->case_sensitive;
 	for (WordState &ws : this->word_index) {
 		if (!ws.match) {
@@ -115,7 +113,7 @@ void StringFilter::AddLine(const char *str)
 					this->word_matches++;
 				}
 			} else {
-				if ((match_case ? strstr(str, ws.word.c_str()) : strcasestr(str, ws.word.c_str())) != nullptr) {
+				if (match_case ? str.find(ws.word) != str.npos : StrContainsIgnoreCase(str, ws.word)) {
 					ws.match = true;
 					this->word_matches++;
 				}
diff --git a/src/stringfilter_type.h b/src/stringfilter_type.h
index a4f6c8c03a..f060c3ca4c 100644
--- a/src/stringfilter_type.h
+++ b/src/stringfilter_type.h
@@ -57,8 +57,8 @@ public:
 	bool IsEmpty() const { return this->word_index.empty(); }
 
 	void ResetState();
-	void AddLine(const char *str);
-	void AddLine(const std::string &str) { this->AddLine(str.c_str()); }
+	void AddLine(const char *) = delete; // prevent implicit construction of string_view from potential nullptr
+	void AddLine(std::string_view str);
 
 	/**
 	 * Get the matching state of the current item.