diff --git a/opts/envfile.go b/opts/envfile.go
index 10054c896c..69d3ca6f60 100644
--- a/opts/envfile.go
+++ b/opts/envfile.go
@@ -18,5 +18,5 @@ import (
 // environment variables, that's why we just strip leading whitespace and
 // nothing more.
 func ParseEnvFile(filename string) ([]string, error) {
-	return parseKeyValueFile(filename, os.Getenv)
+	return parseKeyValueFile(filename, os.LookupEnv)
 }
diff --git a/opts/envfile_test.go b/opts/envfile_test.go
index 6302263848..bda9dcb6e7 100644
--- a/opts/envfile_test.go
+++ b/opts/envfile_test.go
@@ -139,3 +139,40 @@ another invalid line`
 		t.Fatalf("Expected [%v], got [%v]", expectedMessage, err.Error())
 	}
 }
+
+// ParseEnvFile with environment variable import definitions
+func TestParseEnvVariableDefinitionsFile(t *testing.T) {
+	content := `# comment=
+UNDEFINED_VAR
+HOME
+`
+	tmpFile := tmpFileWithContent(content, t)
+	defer os.Remove(tmpFile)
+
+	variables, err := ParseEnvFile(tmpFile)
+	if nil != err {
+		t.Fatal("There must not be any error")
+	}
+
+	if "HOME="+os.Getenv("HOME") != variables[0] {
+		t.Fatal("the HOME variable is not properly imported as the first variable (but it is the only one to import)")
+	}
+
+	if 1 != len(variables) {
+		t.Fatal("exactly one variable is imported (as the other one is not set at all)")
+	}
+}
+
+// ParseEnvFile with empty variable name
+func TestParseEnvVariableWithNoNameFile(t *testing.T) {
+	content := `# comment=
+=blank variable names are an error case
+`
+	tmpFile := tmpFileWithContent(content, t)
+	defer os.Remove(tmpFile)
+
+	_, err := ParseEnvFile(tmpFile)
+	if nil == err {
+		t.Fatal("if a variable has no name parsing an environment file must fail")
+	}
+}
diff --git a/opts/file.go b/opts/file.go
index 281905949b..1721a46ef9 100644
--- a/opts/file.go
+++ b/opts/file.go
@@ -21,7 +21,7 @@ func (e ErrBadKey) Error() string {
 	return fmt.Sprintf("poorly formatted environment: %s", e.msg)
 }
 
-func parseKeyValueFile(filename string, emptyFn func(string) string) ([]string, error) {
+func parseKeyValueFile(filename string, emptyFn func(string) (string, bool)) ([]string, error) {
 	fh, err := os.Open(filename)
 	if err != nil {
 		return []string{}, err
@@ -53,17 +53,23 @@ func parseKeyValueFile(filename string, emptyFn func(string) string) ([]string,
 			if strings.ContainsAny(variable, whiteSpaces) {
 				return []string{}, ErrBadKey{fmt.Sprintf("variable '%s' has white spaces", variable)}
 			}
+			if len(variable) == 0 {
+				return []string{}, ErrBadKey{fmt.Sprintf("no variable name on line '%s'", line)}
+			}
 
 			if len(data) > 1 {
 				// pass the value through, no trimming
 				lines = append(lines, fmt.Sprintf("%s=%s", variable, data[1]))
 			} else {
 				var value string
+				var present bool
 				if emptyFn != nil {
-					value = emptyFn(line)
+					value, present = emptyFn(line)
+				}
+				if present {
+					// if only a pass-through variable is given, clean it up.
+					lines = append(lines, fmt.Sprintf("%s=%s", strings.TrimSpace(line), value))
 				}
-				// if only a pass-through variable is given, clean it up.
-				lines = append(lines, fmt.Sprintf("%s=%s", strings.TrimSpace(line), value))
 			}
 		}
 	}
diff --git a/opts/parse.go b/opts/parse.go
index 679759deda..70b60e142f 100644
--- a/opts/parse.go
+++ b/opts/parse.go
@@ -19,10 +19,10 @@ func ReadKVStrings(files []string, override []string) ([]string, error) {
 // present in the file with additional pairs specified in the override parameter.
 // If a key has no value, it will get the value from the environment.
 func ReadKVEnvStrings(files []string, override []string) ([]string, error) {
-	return readKVStrings(files, override, os.Getenv)
+	return readKVStrings(files, override, os.LookupEnv)
 }
 
-func readKVStrings(files []string, override []string, emptyFn func(string) string) ([]string, error) {
+func readKVStrings(files []string, override []string, emptyFn func(string) (string, bool)) ([]string, error) {
 	variables := []string{}
 	for _, ef := range files {
 		parsedVars, err := parseKeyValueFile(ef, emptyFn)